Tag Archives: Antennas

Accessories, Antennas, Articles, How To, News, Portable, QRP

Construction Notes: VO1DR Monopod Antenna Mount

8 Comments

Many thanks to Scott (VO1DR) who shares the following guest post:

Construction Notes – VO1DR Antenna Mount for Camera Monopod

by Scott Schillereff,  VO1DR

Further to my article about radio during trip to Portugal, a number of readers asked for details on how I mounted my whip antenna system to my camera monopod for /P use.  Here are some photos and notes on this.

General notes:

  • This is a “straight-through” design.  Just direct connections from the BNC center pin to whip (via brass nut), and BNC housing to radial connector.
  • This is not a cook-book construction article, rather just a show-and-tell of how I built mine.  You can use what you have on hand to build something similar.
  • I suggest you start with your telescoping whip, so you know the size and threads for mounting bolt.
  • You could use any type of connector for the radial (wingnut, knurled nut, spade lug, alligator clip, whatever you like).  I prefer banana jacks since a) I can push in the radial banana plug fast, b) the plug is a weak release point (pulls apart if someone walks into the radial), and c) I can easily attach additional radial wires, if desired.
  • Use a strong case (metal clamshell or cast aluminum work well).  With the whip extended, there can be substantial forces (bending moment) from wind or handling. A tiny plastic case would be fractionally lighter but might fail.
  • For size, the one I used (25 x 25 x 50 mm; 1” x 1” x 2”) is about as small as I would go.  It needs to have a big enough footprint to sit firmly on a camera mount fitting.
  • Use high heat (e.g., Weller 100-140 W solder gun) when soldering the center pin wire to the brass whip mounting nut.  Solder the wire to the brass nut before you epoxy the nut.
  • I custom made the white plastic insulating bushing (where whip screws in). This was from a nearly-right bit from my junk box.  You can be creative here.  You could also epoxy on short piece of close-fitting, thick-walled PVC pipe around the outside of the whip mounting hole as a supporting sleeve to give some lateral support to whip when it is screwed in.
  • Dry-fit everything (before epoxying) to make sure nothing touches that shouldn’t and you can screw in the camera nut and whip fine.  Test proper continuity of center pin and radial connections to BNC fitting.  Once glued, there’s no going back!
  • For surfaces to be epoxied (metal nut sides and bottom, insides of mounting case), slightly roughen with sandpaper or jewellers file, then clean with isopropyl alcohol and Q-tip.  This will increase adhesion and strength.
  • Use good-quality, high-strength, long-cure epoxy (e.g., JB Weld), not el-cheapo 5-minute epoxy from the Dollar Store.  LET THE EPOXY COMPLETELY CURE BEFORE MESSING WITH IT!  Just walk away from it for a day… (your patience will be rewarded).

Figure 1 – VO1DR Antenna Mount, clamped onto top of monopod.  Coax goes to BNC on left; whip screws into top; raised radial connects by banana plug on right

Figure 2 – Antenna mount unclamped from top of monopod.  The black plastic fitting (at right, with wedge-shape) fits into slot on platform at top of monopod (at left) and clamps in with cam arm.  Large steel screw attaches wedge fitting to antenna mount case. Ruler shows scale of things.

Figure 3 – Antenna mount case (right) unscrewed from camera mount fitting.  Steel screw is standard camera mount size (1/4-20 thread size).  Black silicone cap keeps dust out of BNC connector.  If your camera mount does not have a detachable wedge fitting (like the one on the left), you would simply screw the camera mount screw directly into the bottom of the antenna mount case.

Figure 4 – Top of monopod dissembled to show (clockwise from top): black monopod tube with telescoping whip stored inside (stainless steel with 10 mm brass mounting bolt), antenna mount case, detachable camera mount fitting, and round top plate of monopod.  For my monopod, I had to remove one tiny screw and apply gentle torque to break a weak glue joint of this round piece on top of the monopod leg.  It remains a snug hand fit (no screw needed).

Figure 5 – Fully assembled whip antenna mount with wiring.  Radial (blue wire) with tie-off cord (yellow) at left; RG174 coax (5 m) at right.  Whip is only ever screwed in hand-tight.  Deploying in the field, I first tie off the monopod to something (park bench, picnic table, fence, tree), then screw the collapsed whip into the antenna mount and clamp mount on top of monopod, then plug in radial and tie the yellow cord off to something (straight out at 2 m height or slope down to ground anchor), and finally connect the coax to the rig.  When all in place, I carefully raise the whip (slowly, with two hands to reduce bending forces).  Take-down is all in reverse.

Figure 6 – Detail of antenna mount case.  Case is 50 mm x 25 mm x 25 mm aluminum clam shell box with square metal end plates.  These end plates are screwed in to hold the two halves together.  White plastic bushing provides additional lateral support for the whip when it is screwed in.  The bushing is glued to outside of case with CA (Krazy) glue.

Figure 7 – Inside of antenna mount case.  On left, a ¼-20 steel nut is epoxied to inside of case with strong JB Weld epoxy.  In main case, a 10 mm brass nut is epoxied to inside of case with an insulating washer beneath.  This brass nut connects to the whip and is “hot”, so must be insulated from the black aluminum case.  Yellow wire connects center of BNC to brass nut (soldered).  Black wire connects ground side of BNC to radial banana jack.  Use plenty of epoxy; there is a lot of force exerted on the steel and brass nuts.

Figure 8 – Detail of inside of case.  Note separation of banana jack solder post and edge of 10 mm brass nut.  Solder yellow wire to nut before epoxying in nut.

Hope you find this useful.  Just use what you have on hand and some ingenuity to make yours!

Best 72, Scott  VO1DR

Antennas, Field Day, Guest Posts, Morse Code, POTA, QRP

Experimenting during Field Day 2024

6 Comments

by Vince (VE6LK)

Field Day 2024 started out with the best of plans to be spent with the best of friends and ended up totally different – and, unexpectedly, I had a hoot! With my carefully made plan behind me, my new last-minute plan was to run solo for Field Day in the backcountry of Kananaskis Country and bring along my new-to-me Nikon D3400 and lenses and rekindle my interest in (D)SLR photography at the same time as doing some experimentation with radio gear.

I grew up in a home with a scratch-built enlarger and a darkroom, so a love of taking pictures has been with me for a long time. My Father taught me patience to get the shot as he would set up a 120 format bellows camera on an air-triggered remote release to get closeups of chipmunks while we were camping, a process that took hours and yielded excellent results. My Brother, AG7GM, has attempted to instill within me the basics of composition, rule of threes and such and his wonderful skill in editing both stills and live video. While I have plenty of patience, with composition I think I’m fair to middling at best.

Thus photography has always been on my mind.

With a recent sale of a few ham radio related items, I had fun money, so just for fun I started looking [on Thursday before I activated] at used DSLRs and was shocked at how much camera I can get for such a relatively low cost compared to new. I had said once, 25 years ago when I divested out my 35mm kit, that when I could get a DSLR with a 25 to 300mm lens for <$500 I’d jump in… and finally that day is here, even if it means carrying two lenses. Of course, I started looking on the day before Field Day for deals – and scored them too! 🙂 Around these parts, good quality pre-owned consumer grade DSLRs are easily available. I purchased this as much for still photography as for ability in shooting high-quality video for my YouTube channel.

These peaks form part of the border between Alberta and British Columbia to the west

For me, Field Day has always been about the experimentation rather than chasing points. Trying new things. Changing up from the normal way I operate in the field. Comparing, analyzing and making notes as I go.

For example, and as a tribute to Chip Margelli K7JA (SK) after corresponding with his brother David, last year I attempted to wet a piece of string and see if the KX3’s tuner would match it and radiate a signal. Chip was known for many things, among them his proficiency in CW as he demonstrated on The Tonight Show with Jay Leno in 2005. David told me that he and Chip would do crazy and fun experiments like loading up clotheslines and wet string to experiment .. and it fostered a new direction I could take each FD and on some days between. The string experiment was a failure last year but I haven’t given up yet!

This year, I wanted to work with a few different antennas and a Charmast 100W battery pack from Amazon along with a USB-C PD 12v power cable for my KX3 [note: Amazon affiliate links!].

I wanted to know, in no uncertain terms, that the Charmast would or wouldn’t be as quiet as my trusty Talentcell LiFePO4 pack. The Charmast is also used in my field soldering kit with a Pinecil as it delivers USB-C PD. What better way to test this out than to head as far away from noise sources as possible, see the Canadian Rockies in their early summer glory with snow on the peaks, rivers running high (and cold) and the sun in the sky? Just for grins I would ensure that I was in POTA entities while doing Field Day.

Continue reading Experimenting during Field Day 2024 →

Accessories, Antennas, Comparisons, New Products, News, Portable, POTA, QRP, SOTA

Mike compares the new Explorer POTA20 with the venerable SOTAbeams Carbon 6 Mast

6 Comments

Last week, I ran into my good friend Mike (KE8PTX) at Hamvention, and he was bursting with excitement over a new product he’d just purchased: the Explorer POTA20 Carbon Fiber Mast at GigaParts.

Mike is a massive fan of the SOTAbeams Carbon 6 telescoping pole and has been through two of them over the years he’s been doing field radio work. He told me that the new Explorer POTA20 is even better than the Carbon 6.

I don’t think Mike knows it yet, but after his recommendation, I ordered an Explorer mast—it’s backordered, so it’ll be a month or two before it ships.

Mike took this photo of his mast from a POTA activation this morning. You can see the mast left of the dead tree.

Mike is also a brilliant designer and has made a 3D-printed tent stake holder that fits on the end of both of these poles. He told me that these 20′ carbon fiber masts are so lightweight that there’s no need for guying the pole, even in fairly windy conditions. His simple tent spike is all that’s needed to hold a carbon fiber mast in place.

Videos

In the following video, Mike compares the Carbon 6 with the new Explorer mast and speaks to the utility of using a tent spike to secure the mast:

Thank you, Mike, for sharing this video and the tip about the new Explorer mast!

Again, it’s currently backordered at the time of posting, but you can place an order at GigaParts. The price is $79.95 plus shipping.

Accessories, Field Radio Kits, Guest Posts, Morse Code, News, Portable, POTA, QRP, Travel

Planning a POTA Babe Trip – Part 2

9 Comments

(Note: I cut my Florida POTA trip short as I needed to take care of some personal business. I apologize for the change of plans and the inability to communicate that to y’all. I appreciate everyone’s support of the trip and the QSOs of those who hunted me. Articles will be forthcoming for those activations in the near future.)

Those of you who have followed my journey on QRPer know that I wrote an article about my kit for the trip I took last summer to Nova Scotia. Since then, what ham radio equipment I take with me has changed, partially because I am not flying to a different country far from home and partially because of my experiences with what I generally do and don’t need. I thought I’d share what my kit currently looks like for the spring-break Florida trip.

Here is a photo of what ham radio-related gear I am taking on my Florida POTA trip. We’ll first look at what I have in each section of the Elecraft bag I take with me and then a few items that do not fit in this bag but are still along for the ride.

When I purchased my KX2, I also purchased the Elecraft bag. Though the bag is bulky in its profile, it was a worthy purchase due to the amount of stuff it can store in one place in a well-organized manner.

The bag has three compartments.

In the first compartment is my main man, Craig, my KX2. He is the rig I use for all my QRP adventures out and about. I do have a protective cover I purchased for him but haven’t installed yet. I have a fear of messing with electronics and, though installing the shield isn’t rocket science, the project seems overwhelming enough that I haven’t tackled it yet.

Also in this first compartment are my throw bag containing an arbor line and throw weight, some S-carabiners, my homemade radials for the AX1, the tripod mount for the AX1, and a pencil and earbuds. I find I copy CW much better when I have a headset of some sort.

In this compartment, I used to have a back-up key. However, in its place is a new single-lever paddle from CW Morse [QRPer affiliate link]. I am using this key because it is wired to be a cootie or a paddle via an internal switch. I discovered my KX2 doesn’t balk at using this key like a cootie unlike when I use the CW Morse SP4. I desire to use QRP for more than POTA, specifically for SKCC and calling CQ for ragchews. SKCC requires a mechanical key and, as the cootie is my favorite key, this new key should fill the need  I discovered the last time I visited Skidaway Island.

In the second compartment, I have the AX1 and the Tufteln EFRW antenna. Those of you who have read my articles know I generally deploy the Tufteln EFRW antenna. On this April Florida trip, I plan to use the AX1 and the Chelegance MC-750 more often in preparation for my summer POTA trip. I anticipate I’ll be limited by terrain and park rules from deploying an antenna in a tree so more experience with verticals will be helpful.

In the third and final compartment are some odds and ends: neon pink flagging tape, an allen wrench for adjusting my CW morse keys, some twine, a short length of wire with an alligator clip on the end, two shock bungee cords, the cord for my CW Morse single-lever key, and a splitter for the headphone jack. I’ve used all these items (except the cord for the new key) at one time or another so I don’t want to leave the house without them.

Here are items I am also taking that don’t fit in the Elecraft bag.

The Tufteln kneeboard, POTA flag, and a notebook. I really like using pencil and paper for my POTA logs. I hold my key in the left hand and send with the right. For some reason, juggling that with paper is more manageable to me than logging in my phone or a laptop. The one thing I miss out on by doing that, though, is not knowing people’s names except those I’ve encountered many times. (And even then I forget names in the busyness of an activation so if I do, please forgive me.) I like to thank people by name at the end of the QSO rather than just their call sign if I know their name. I learned to do this in SKCC exchanges and I think it is a respectful and genteel practice. The one advantage I see to using a logging program is that I could do that with every QSO.

In a Tom Bihn bag, I have my RG-316 coax in three lengths (10’, 20’, and 50’), a short bungee cord, a stereo connector, and a newer version of the SP4 (aka The Minion).

Also coming along for the ride is the Chelegance MC-750. [QRPer affiliate link]

The last pieces of equipment I am bringing are for the first park I will visit – Lafayette Wildlife Management Area. In areas that allow hunting, Daisy and I wear blaze orange, even in the off season. Though as hams we try to be law abiding, we need to remember there are others out there who are not. When it comes to areas in which hunting is allowed, it is wise to wear blaze orange year-round because hunting violations due happen.

There you have it – the POTA Babe’s current QRP kit. I have one last question to address in this series – how I plan my trips. To find out, stay tuned…

Antennas, Guest Posts, News, Portable, QRP, Videos

Scott’s Self-Supporting Random Wire Antenna System

5 Comments

Many thanks to Scott (KK4Z) who shares the following post from his blog KK4Z.com:

K4SWL+ Antenna

by Scott (KK4Z)

On a recent post on QRPER.com, Teri KO4WFP was at a park in Florida that did not allow wires (or anything else) in their trees. Many POTA activators use End Fed Half Wave antennas which usually require one end in a tree. While it doesn’t happen at all parks, not being able to hoist your antenna could bust an activation.

I realized this may happen to me even though Georgia appears to be pretty lenient when it comes to such matters, I decided to switch to a park friendly antenna. I have been a fan of QRPER.com for quite some time and occasionally Thomas will repost something from my humble blog. That being said, it was K4SWL that got me started using a random wire antenna. My basis for my antenna was his speaker wire antenna which was a 28.5’ vertical antenna with a 17’ counterpoise. I used it a few times in that configuration and then started to modify it. I call this antenna my K4SWL+.

Some of the differences are I use a push-up pole to get the antenna in the air and at the base I use a 9:1 UnUn and a 1:1 Choke to keep RF out of the radio. A random wire antenna can feed RF back into the coax.

The wire is 14 ga. coated flex weave from The Wireman. This was left over wire from some other antenna projects. When I started this project I was using 22-24 ga. coated wire from SOTABeams but realizing there was no need to save weight, used the heavier wire. This allows me to dual purpose the antenna both for FunComm and EmComm. The insulator at the top is 3D printed with my call-sign and the base is U-type lugs. I find these are the best as I do not have to take the nut off of the antenna studs and if pulled hard will come loose instead of damaging the UnUn. I connect the antenna to the top of the push-up pole with a small Nite-eze “S-biner” size 1.

The 9:1 UnUn comes from Palomar Engineering. I have already created a blog post about how to build it and it can be found here: https://kk4z.com/2022/05/28/91-unun-qro/

Part of this blog post was to bring the different components together into one blog post.

The 1:1 Choke can be found here: https://kk4z.com/2022/08/15/lightweight-choke-balun/

I made two different types but I found the second works much better.

The project is pretty easy, the only caveat is to pay attention to what wire goes where. Putting it all together, you need a push-up pole, a Flag holder and maybe a trailer hitch extender. I will provide links below. The Flag Pole holder I used was not available so the link I used is a probable substitute. I have a trailer hitch on both my truck and my camper, When I pull into a campsite I have a choice of which hitch to use to keep my antenna clear from the trees. With the antenna up, I wrap the antenna wire around the push-up pole from tip to base, to prevent the wire from sagging near the tip. I attach the UnUn and choke to the mast with Stretch Velcro Straps. With my antenna up I have park employees drive by me all day along. Most of the time we exchange a friendly wave and occasionally one will stop by for a chat. I have had zero issues with this antenna at any of the parks I have visited.

How does it play? It has pretty much been a main antenna for just about all of my POTA activations. You can go back through my blog post and see what equipment I used with the antenna and the accompanying QSOMap. You do need an antenna tuner with this antenna and I typically use an LDG Z-11 Pro which I’ve had for 15+ years. The antenna tunes up from 80 to 6 meters and I have run the power as high as 65 watts. I normally run 10-35 watts depending on band conditions. I have tried it on 160 meters and while I can get a match, I don’t think much RF is leaving the antenna. I’ve made a few contact with it on 160. If you like to work 160 meters during a POTA activation, I suggest a Chameleon EmComm II with a 60’ antenna and a 50’ counterpoise. I run it as an inverted L with the apex about 20’ up my push-up pole and the end sloping down to something not a tree. Last time I tied it to the lantern stand at the campsite. It worked pretty well and I was able to make contacts on 160.

Video:

Click here to view on YouTube.

If you’re looking for an antenna that you can set up almost anywhere, with little or no hassles, take a look at this one. Don’t forget to check out the short video above. 73 — Scott

Antennas, Field Reports, New Products, News, Portable, POTA, QRP, SSB, Videos

SSB and CW QRP POTA: Testing my new KM4CFT End-Fed Antenna Kit!

12 Comments

A few weeks ago, I mentioned that Jonathan (KM4CFT) sent me one of his new QRP end-fed half-wave/random wire antenna kits.

When my friend, Alan (W2AEW), caught wind that I planned to buy some 26AWG wire for this build, he sent me a spool of wire from a large reel he’d recently picked up at a hamfest.

What a nice guy! The blue wire is absolutely ideal for portable antennas.

Being the nice guy he is, Alan actually published a video about building Jonathan’s antenna kit on his YouTube channel. I highly recommend watching it!

Before I received the kit, I already knew what type of antenna I’d build: a 30 meter end-fed half-wave (EFHW) linked with a 40 meter extension. This antenna design has been on my mind for some time and Jonathan’s kit was the perfect excuse to build one.

Why a 30M EFHW with a 40M extension? Because a 40M EFHW gives me excellent SWR matches on 40, 20, 15, and 10 meters without needing an ATU.  A 30M EFHW gives me matches 30 and 17 meters.

Thus, with one linked wire antenna, I can cover 40, 30, 20, 17, 15, and 10 meters! That’s a lot of bands!

And since the antenna needs no extra matching, it’ll work with my transceivers that lack an internal ATU.

The Mountain Topper MTR-5B I acquired earlier this year.

In fact, I originally thought about this antenna design to use with my Mountain Topper MTR-5B which covers 40, 30, 20, 17, and 15 meters.

I built this antenna by first trimming it for a 1:1 match on 30 meters including a loop and strain relief to attach the extension.

When I was satisfied with my 30M EFHW, I then made the 40M extension, attached it to the 30M section with 2mm bullet banana connectors, then trimmed the antenna for a 1:1 match on 40M.

I spent the better part of 60 minutes trimming this antenna. I feel like patience really pays off because it’ll set up the antenna for good matches on all of the upper harmonics. Admittedly, I was a bit pressed for time that day, so I only tested this antenna in one configuration (an inverted vee shape) so hadn’t checked the SWR as a sloper or vertical.

My advice is to aim for a 1.3:1 or better match on 30M and 40M–that should be very doable if you wound your transformer correctly.

This was my first attempt at making in-line links, so I wouldn’t consider link my method as a “best practice”–rather, check out K7ULM’s guidance for making in-line links. Continue reading SSB and CW QRP POTA: Testing my new KM4CFT End-Fed Antenna Kit! →

Antennas, News, Portable

GW4OKT’s “Cheap & Cheerful Telescopic SPOTA Antenna”

11 Comments

Many thanks to Keith (GW4OKT) who shares the following guest post:

Cheap & Cheerful Telescopic SPOTA Antenna

Available on eBay for around £45, this 5m whip with a ground spike and counterpoise/radial.

Sold as a QRP antenna, yet in the specs, quote it as ‘able to withstand 300W’, I think I will stay at 5-10W to be honest!

Well, I used it on two POTA activations on the 11th of November, coupled to my KX2 and internal ATU. You can obviously adjust the whip for best match, but I was lazy and left it at full height.

Most QSOs where on 20m and 17m.  The seller quotes that it will tune 20m to 10m and I found this to be correct.  It will also ‘tune’ on 30/40m, but don’t expect decent performance.

This is truly a cheap compromise antenna, but I was surprised how reasonable the build quality was!   As you can see, it doesn’t take up much space, the aluminium ground spike is 10” long including the threaded portion.

The closed up whip is 20.25 “ including the threaded portion.

The ribbon counterpoise is also 5m long and is terminated with an eyelet that attaches to the ground spike threads.  I did consider splitting the ribbon to make a fan pattern, but thought it would be pretty messy to deploy an store, I kept it simple and still achieved good results!

This is a handy standby antenna, or for holiday activations, but bring your tuner along!

72 de GW4OKT

eBay Links:

Antennas, How To, News, QRP

Jan’s Unun and Balun antenna PCBs

7 Comments

Over on Mastodon, Jan (DG1JAN) posted a few images of a PCB-based antenna project he made available on github. At my request, Jan kindly shared the following information so you can order your own PCBs with design files he has made available.

Jan writes:

Hello Thomas,

I mostly do portable operation (SOTA, COTA, WWFF,…) and I
like playing around with different antennas (EFHW, Linked Dipoles, OCFD…).

So I came up with a little PCB some time ago that you can use as an UnUn (1:49, 1:9) or BalUn (1:1, 1:4) in different configurations.

I’ve put this under CC License so everybody can reuse or modify the Design (PCB Files in Kicad-Format) or order PCB from any Manufacture (e.g. like JLCPCB) by using the Gerber-Zip-File in the repository.

Please have a look to the Project Page on github for details and source-files: https://github.com/DG1JAN/UniBalun

In addition I’ve done some variations of the PCB, e.g. as a
“UnUn only” variant:
https://github.com/DG1JAN/AntennaPlayground/tree/main/UnUn_BNC_1.2

Or a “micro” variant of a UnUn:
https://github.com/DG1JAN/AntennaPlayground/tree/main/microUnUn

There are some videos from (mostly) German OMs on YT about the build and usage.

vy 73 de Jan, DG1JAN

Thank you so much for sharing this, Jan! Readers, it’s pretty affordable to use a service like OshPark to order a few of these PCBs. Simply upload the provided Gerber files and they’ll make them for you.

Antennas, Guest Posts, How To, Portable, QRP, SOTA

A Portable Oblong Antenna for 2 Meters

5 Comments


Many thanks to Andrew (VK2ZRK) who writes:

Hello Thomas,

The area I live near Canberra in Australia has many SOTA summits that are easily activated on 2m with a HT. That said a good antenna always helps. The 2m oblong antenna is very popular in these parts. It is easy to make, light to carry and packs small. It is horizontally polarised.

This is the second oblong I have built. I gave my dad VK4FASR my first one and have finally built another. I mostly use the bottom of the band for SSB/morse, the middle for APRS on 145.175 and 145.500 for SOTA. The antenna is cut accordingly.

References:

Andrew VK1AD
https://vk1nam.wordpress.com/2019/09/29/antenna-project-2m-145-mhz-rectangular-loop/

Peter VK3YE
https://youtu.be/Nyttl277ehs?si=9M5mP-KlxTGln0Tm

PARTS LIST
(Sorry about the lack of Freedom units)

    • 8mm fibreglass tube.
    • 8mm ID kite nocks (both from a kite supply).
    • Double walled glue lined heat shrink.
    • 2200mm Antenna wire – DX Commander in this case.
    • 2mm ‘ZingIt’ dyneema.
    • A BNC to banana adapter.

Assembly

I cut the tube so the centre to centre distance between the holes in the kite nocks was 360mm as per Andrew VK1AD’s instructions.

With the wire I started with 2200mm and trimmed until I had the best SWR at 145.000 when I lost my nerve and stopped cutting. [See photos below.]

Everything is held together with the glue lined heat shrink.
The top tube includes a little loop made from the ZingIt to suspend the antenna. Total weight is 102g.

The 2mm ZingIt can hold about 200Kg. I hope the pics make sense

73
Andrew VK2ZRK

Photos with detail

Antennas, Articles, Guest Posts, News

Chameleon MPAS Lite: Using the coax shield as a counterpoise and how this might affect directionality

13 Comments

Many thanks to Dale (N3HXZ) who shares the following guest post:

Portable Operation Using a Vertical Antenna Without a Counterpoise Wire!

by Dale (N3HXZ)

In a previous article that Thomas was kind enough to post, I ran experiments to determine if the counterpoise wire orientation of the Chameleon MPAS LITE antenna system in the vertical configuration in any way shaped the antenna pattern.  The configuration of the antenna is shown below.

The system consists of a 17’ telescoping whip antenna, a matching transformer, a 50’ coax cable with an in-line RF choke, and a counterpoise wire (60’ long, but unwound to only 25’ for use in the vertical configuration).

Subsequent studies I performed have reinforced my earlier conclusions that the positioning of the counterpoise wire in this setup does not appreciably shape the antenna pattern. One of the comments from my post came from Stephan (HB9EA). He commented on the fact that the coax cable is indeed a counterpoise via the coax shield and that in fact my system set-up had two counterpoises.

It was Stephan’s comment which led me to contact Chameleon Antenna to discuss counterpoises with the MPAS LITE antenna in the vertical configuration. I communicated with the Director of Research and Development group at Chameleon and found out some interesting information that I wanted to pass on.

He mentioned that the system can be used with the coax cable acting as the lone counterpoise as long as the coax cable is at least 25’ long, and preferably 50’ long.  The coax should be spread out and not coiled along any portion of its length. It was stated that the counterpoise wire provided with the product should be used with short-length coax cables.

With regards to a counterpoise orientation shaping the propagation direction, he stated that it is generally accepted that using only the coax as a counterpoise tends to have the antenna pattern slightly favor the direction in which the coax is laid out. Adding the counterpoise wire in a direction opposite to the coax would tend to balance out that pattern. Having the coax and counterpoise wire at some angle to each other introduces variables that make it difficult to determine the antenna pattern.

My initial study had the counterpoise wire oriented at an angle to the coax cable.  I mentioned that my initial study showed that orientation of the counterpoise wire did not seem to appreciably shape the antenna pattern, and he agreed. What is unknown is the overall degree to which the coax cable shapes the antenna pattern with or without use of the counterpoise wire.  This is an area I am currently investigating.

Operating the MPAS-LITE vertical configuration with only the coax cable as a counterpoise was an intriguing thought.

To test it out I teamed up with Jim (KJ3D) for a SOTA activation on W3/PT-003 (Seven Springs). We both deployed the MPAS-Lite with only the supplied 50’ coax cable attached. Coax cables were laid out in a straight line. One cable was oriented southeast, the other one oriented east. We operated on 10 Watts in CW mode. The activation successfully worked all bands from 40M to 10M. I operated an Elecraft KX2 and Jim operated a KX3. The internal tuner of both rigs easily obtained a 1:1 match across all bands.

A map of the QSO’s is shown below. Note that despite the coax cables facing to the southeast and east, we easily worked stations in the opposite directions. Hence any minor shaping of the antenna pattern by the coax orientation does not appear to impede successful communication in all directions.

In summary, the MPAS-LITE antenna system in the vertical configuration utilizing the 50’ coax cable with an in-line RF choke as the single counterpoise has been demonstrated to perform well in the field.

For portable operation where fast deployment and simplicity is paramount, using the furnished coax as a counterpoise is a quick and dirty way to get the antenna erected and on the air with reliable communication capability. Eliminating the counterpoise wire allows for quicker set-up and tear-down, and one less thing to put in the backpack!