Category Archives: Antennas

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, Guest Posts, News, Portable, QRP, Radio Field Craft

Comparing Coaxial Loss in RG-58 and RG-316

40 Comments

by Eric, WD8RIF

I recently decided that I would operate portable during the upcoming ARRL 10 Meter Contest and would combine this operation with a pair of Parks on the Air (POTA) activations, one on the Saturday of the contest and one on Sunday. While putting together my field station for this, I realized I wanted to see how lossy my RG-58 and RG-316 feedline cables were on 10m. Yes, I could have resorted to online charts of feedline losses, and I know that the RG-316 is lossier than the RG-58, but I thought it would be fun and more enlightening to make actual measurements, to empirically determine the losses in my particular coaxial cables.

The two coaxial cables in question are both 25′ in length and both are equipped with BNC male connectors on each end. The RG-58 cable is a high-quality cable that was originally manufactured to be a 10Base2 ethernet cable, but it’s probably now over twenty years old. The RG-316 cable was recently purchased from Tufteln (link) and includes an RF choke near one end.

To make my measurements, I used my Elecraft KX2 (link) to generate RF into an Elecraft DL1 dummy load with RF detector (link), using a digital multimeter to measure the voltage at the DL1’s measurement points. I used the formula that came with my DL1 assembly instructions to calculate the measured wattage:
P = (((V x 1.414) + 0.15))^2)/50

I made measurements in the CW portion of the 10, 15, 20, 40, and 80m bands, with the KX2 set at 5 Watts output.

My first set of measurements was made with the DL1 connected directly to the KX2’s antenna jack using a BNC union:

Direct (no feedline)
Band Volts Watts
10 11.62 5.498
15 11.59 5.470
20 11.61 5.489
40 11.63 5.508
80 11.63 5.508

My immediate observation was that the KX2 appears to be generating more than 5w when it is set to be producing 5w but also that the KX2 output is essentially same from 10m through 80m.

My second set of measurements was made with the DL1 connected to the KX2 through the RG-58 cable:

Direct RG-58
Band Watts Watts
10 5.498 4.809
15 5.470 4.844
20 5.489 5.004
40 5.508 5.184
80 5.508 5.276

My third set of measurements was made with the DL1 connected to the KX2 through the RG-316 cable:

Direct RG-316
Band Watts Watts
10 5.498 4.190
15 5.470 4.322
20 5.489 4.507
40 5.508 4.774
80 5.508 4.959

I was pleased to see to see that both the RG-58 and RG-316 behaved as I expected them to: the loss increased with increasing frequency.

Using the magic of MS-Excel, I created a table of Loss in Watts for both cables, relative to direct connection and to each other:

Direct Difference (Loss) (Watts)
Band Watts RG-58 vs
direct		 RG-316 vs
direct		 RG-316 vs
RG-58
10 5.498 0.690 1.309 0.619
15 5.470 0.626 1.148 0.522
20 5.489 0.485 0.982 0.497
40 5.508 0.324 0.734 0.410
80 5.508 0.232 0.549 0.317

In looking at this table, it was immediately obvious that RG-316 is much lossier than the RG-58, particularly on 10m. By looking at the row for 10m, one can see that I am losing nearly 0.7 watts in the RG-58 but I am losing over 1.3 watts in the RG-316.

For completeness, I added columns for Loss in dB to the spreadsheet:

Difference (Loss) (dB)
Band RG-58 vs direct RG-316 vs direct RG-316 vs RG-58
10 0.582 1.180 0.598
15 0.528 1.023 0.495
20 0.402 0.856 0.454
40 0.263 0.621 0.358
80 0.187 0.456 0.269

This exercise showed me that for my upcoming ARRL 10 Meter Contest POTA outings, I would do best by connecting my antenna directly to my transceiver, if possible, without using either coaxial feedline. If conditions at the operating site require me to use feedline, I will chose the RG-58 over the RG-316.

The tables also tell me that RG-316 is pretty lossy regardless of the band; for my regular field operating, unless I’m planning to do bicycle- or pedestrian-portable operations where weight and bulk is a consideration, I’ll carry RG-58 instead of RG-316. (I purchased the RG-316 specifically for bicycle- and pedestrian-portable operations, and I plan to continue to use the RG-316 for those applications.)

At some point, I will repeat this exercise with RG-8X, a feedline that is very close in size to RG-58, is less lossy, but is also heavier and stiffer.

Antennas, Field Reports, Guest Posts, News, Portable, SOTA

Steve tests the Diamond RHM-8B during a SOTA activation

1 Comment

Testing the Diamond RHM-8B portable screwdriver antenna

By Steve (MW0SAW)

I have seen many amazing K4SWL SPOTA pileups on YouTube using the AX1 antenna and the extension coil. I have fancied trying a small walkie talkie style whip antenna for a while now.

I have a AX1 and KX2, but my Yaesu FT-818 was the radio with a fully charged battery. So I pulled out The Diamond RHM-8B, an antenna I purchased a while ago but never used in the field. It has a BNC fitting and you tune the antenna by sliding the coil up and down for loudest signal and best SWR. They make one very chunky walkie talkie together! Diamond products do have a fantastic air of quality about their construction.

Radio conditions weren’t great, and bands were busy being the weekend of the CQ WW CW contest. So decided to go the my nearest summit that’s amount 12mins in the car and about a 25mins hike up. This was GW/SW-034 Garth Hill. On a clear day you can see out over the Bristol Channel into England, but mist/fog were the order of the day.

I wore the FT-818 and rubber duckie around my neck with the neck strap for a couple of 2m FM contacts, before setting up on 40m SSB sitting on the ground. Without a tablet or chair with me I found it most comfortable to support the radio between my knees.

I was really pleased to get 9 QSOs in the log, some 59 reports, some difficult contacts. Moving on to CW I managed another 8 QSOs with an S2S into Germany.

All the QSOs were UK and mainland Europe, but I was more than happy with the haul for such a small antenna.

So conclusion about the Diamond QRP antenna.

Can you qualify a SOTA summit on a short 1.5m whip antenna? Absolutely, no sweat!

Does it work as well as a full size wire antenna? Of course not. Nowhere close.

However, its makes such a great rapid deploy, ultra packable option with the Yaesu. Not quite as small as a AX1 but you have the bonus of not requiring a tuner. Definitely something for a travel bag if you own a FT-817/818.

Equipment:

Best 73
Steve
MW0SAW/P

Antennas, Digital Modes, Field Reports, FT8, Guest Posts, News, Portable, POTA, QRP

N2YCH’s Top Band POTA Activation Field Report

9 Comments

Many thanks to Conrad (N2YCH) who shares the following field report:

Top Band POTA Activation Field Report

By: Conrad Trautmann (N2YCH)

November 15, 2023

In February 2023, Brian, K3ES, wrote here on QRPer.com about designing and building his own QRP portable random wire antenna he called the VK160 to work on 160 meters to make parks on the air contacts. This was in order to achieve his goal of getting the James F. LaPorta N1CC award where activating on 10 bands at 10 parks is needed. It’s not as easy as it sounds. As an avid parks on the air activator myself wanting to try activating on 160 meters, I built my own antenna based on Brian’s design and used it to get my first contacts ever at a park on the “Top Band.”

The Antenna

Brian used a 9:1 unun that he built himself in his design. Rather than build my own from scratch, I took a short cut and bought a QRPGuys 40m-10m UnUnTenna to use as the starting point for my VK160. Even though it says 40m-10m, it works on 160 meters, as you’ll see.

With shipping, it cost $36.00. It comes with all of the parts you need to assemble the antenna except for the wire. The main thing I liked about the QRPguys design was that the circuit board also doubles as a wire winder, so it’s all self-contained.

I sourced the wire from Davis RF and ordered 200’ of “POLY STEALTH – 26 AWG, 19 0.22000 44.00 STRAND COPPER CLAD STEEL, BLACK PE JACKET.” It cost $50 including shipping. The polyethylene insulation prevents the wire from knotting up. I measured out 144’ for the radiator based on Brian’s design and used the remaining wire as the counterpoise.

The completed antenna

I did a back yard test once it was all assembled and it worked great. For $86, I had created my own VK160. I encourage you to read Brian’s detailed design/build report here.

The POTA Activation – November 14, 2023

Now that I had completed building and testing the antenna, the next challenge was how to actually put it to use at a park. 160 meters doesn’t really come to life until dusk or after dark. In Connecticut, most state parks close at dusk. The park rangers clear the parks to close them at the best time to activate the band. However, there is one park nearby my QTH, the Stuart B. McKinney National Wildlife Refuge, K-0228, that has an annex called the Great Meadows Unit in Stratford with a nice parking lot that is not gated and has no posted hours. I arrived and set up at sunset, around 4:30 pm ET and operated from 5 pm until 6 pm. It gets dark here early in the Northeast US in November.

Another challenge is how to manage and string up 144’ of wire. Brian suggested an inverted V over a tree branch in his write up. There were no trees nearby, so instead I used a Spiderbeam fiberglass pole secured to my Jeep to get the feed point up in the air about 25 feet. I used RG58 cable from the feed point to the radio.

Spiderbeam fiberglass pole supporting VK160

Finally, I used one of my $3.00 Home Depot electric fence posts to secure the far end to keep it tight and up in the air and set up the antenna as a sloper. I laid out the counterpoise on the ground under the sloping wire.

By the time I had all of this set up, it was getting dark. I connected my Elecraft KX3 to the other end of the RG58 cable and to my surprise and delight, I was already receiving stations.

My KX3 has a built-in ATU and one tap of that ATU button and it tuned to 1.0:1. I started the activation right at 5 pm local time and in about 15 minutes, I had six QSO’s on 160 meters.

The PSK Reporter map showed me being received by stations on the dark side of the gray line in the Northeast. It was pretty much what I expected for QRP power on the low frequency. Then, the next ten minutes things were quiet. It appeared I had gotten everyone who could hear me.

Since this is a random wire antenna, it should work on all bands so I decided to test it on 80 meters. Again, the KX3 tuned right up and I got six more QSO’s. I was surprised to see Del, N2NWK from Washington, DC pop up on JT Alert. I have a an alert set for stations calling CQ POTA. Del was also at a park. I called and he answered and we ended up with a park to park. Anyone who knows Del knows that when you hunt him, he’s usually activating at a two-fer, at least. When I checked my hunter log afterwards, I saw four parks listed from him (a four-fer?).

At this point in the activation, I had gotten the ten QSO’s that I needed to call the park activated. I thought, let me try the VK160 on 60 meters. I re-tuned the KX3 and got five more fast QSO’s. The antenna worked great.

Before I packed up, I decided that I really wanted at least ten contacts on 160 meters, which was my original goal. I went back to 160 meters, now close to an hour later than when I began the activation, and easily added five more new QSO’s to the log. Maybe propagation had changed the later/darker it got or some new hams were on the band who weren’t on earlier, but I was satisfied to have gotten more than 10 on the top band.

The Results

Here’s how I did. Green pins are QSO’s on 160 meters, blue pins are 80 meters and the pink ones are 60 meters (click image to enlarge).

Equipment List

Conclusion

The “Top Band” activation was a success! The VK160 worked flawlessly, thank you Brian, K3ES for posting your design and providing the inspiration to activate on 160 meters.

My POTA “My Stats” page now shows 11 digital QSOs on 160 meters that I didn’t have before. I love conquering new challenges and given the challenge of going mobile with an antenna that will actually work and tune up on that low of a frequency at a park that won’t make you leave at sunset, well… that was quite an accomplishment!

Thank you to the 22 hunters (11 on 160 meters) who helped make it a success, including my friend Del, N2NWK in Washington, DC.

Conrad, N2YCH and Del, N2NWK
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, News, QRP

The Best Mountain Topper Antenna: How to build lightweight, in-line links

32 Comments

Many thanks to Dick (K7ULM) who shares the following guest post:

The Best Mountain Topper Antenna

(And a modification that makes it a little better)

by Dick (K7ULM)

When I decided to pursue HF radio, I had already decided to learn Morse Code.  Since learning code on my own wasn’t working, I enrolled in CW Academy classes.   Nearly everyone that I met in the CW Academy classes, plus my Elmer, were all involved in QRP portable ops as well.  A common theme among them all was using efficient, lightweight, easy to deploy antennas.

New to ham radio, QRP, and antennas.  I started to research antennas that fit that set of criteria.  Of course, I stumbled onto K6ARK, Adam Kimmerly’s YouTube video on building an ultralight 40m EFHW.  I accumulated the parts and built an EFHW for 40m.  After tuning the antenna for the lowest SWR, I connected it to a KX3 and contacted hams in Long Island, NY and Atlanta, GA with 12watts using SSB.  I was hooked on QRP and Adam’s antenna design.

When the instructor in my CW Academy class asked what goals each of us had for ham radio, I realized that I had no real goals.  So, I told the group that I wanted to assemble a portable QRP kit that weighed under one pound, and I wanted to operate portable CW from my elk hunting camp in the fall.  The sub-one pound HF kit was inspired by SOTA guru and legend, Fred Mass, KT5X.   I ordered an MTR-3B (Mountain Topper 3b – a QRP CW transceiver), which arrived 2 days before I left for elk camp.  The sub one pound HF kit had become reality.

At elk camp, I was a little distressed that I couldn’t work 30m with the EFHW, but 20m and 40m were a great combination.  Three nights later I was laying on a cot in a canvas wall tent in elk camp scanning the bands and trying to decode signals as I found them.  I heard one signal calling CQ for a long time and decided to try to answer him with my very limited CW skills.  I was able to get the minimum information to make an official QSO.  Looking up the contact’s information on QRZ, I found that it was Lloyd, KH6LC in Keaau, HI, 3000+ miles from elk camp.  Hawaii worked on 5 watts.  I was totally hooked on QRP and CW.

The only problem with the 40m EFHW, is that it doesn’t tune up easily on 30m.  Adam’s 40m EFHW design is excellent, and I wanted to stay with his build design, so I concluded that I needed to put a 30m link in mine EFHW to cover 40m, 30m and 20m without the use of a tuner.   My first effort on building a 30m link worked well but it was heavy and rigid which made it hard to store.  Eventually I created a design for the link that met my goals.

How to build lightweight links

My goals for a link on a lightweight EFHW are that it needs to be lightweight and flexible for easy storage.  It should also be relatively clean in design to minimize the chance of hanging up in trees and bushes while deploying and retrieving the antenna.

The materials for the link design that are currently working the best for me are as follows:

  • Attwood 3/32” tactical cord.
  • Heat shrink tube.
  • Superglue.  Gel type is the least messy.

2mm bullet connectors, or a more solid connection, red knife disconnects from Aircraft Spruce and Specialties Co. https://www.aircraftspruce.com/catalog/elpages/knifedisc.php

The knife disconnects idea is from Charlie Brown of Red Summit RF.  They are worth looking into.  They are my current choice of connector although the bullet connectors are working OK.

The installation of this link is fairly simple.

The first step is to tune a 30m section of wire on your preferred transformer.  The narrow 30m band will normally be well below 1.5:1 across the entire band, which is awesome.  I have found that it is about 32’ 7” of wire for my deployment style and soil conditions.  Your mileage will vary.  You can cut this into an existing antenna but, plan on adding a piece of wire to the end of the antenna to retune it for 20m and 40m.  For an existing antenna, measure the overall length from the transformer to the end of the antenna prior to cutting in the link.  You will use this measurement to restore the overall length of the antenna for the 40m EFHW.

Step two is to cut two pieces of heat shrink tube that will fit over your selected antenna wire and the 3/32” cord.  Slide one piece of tube onto the newly tuned 30m wire and the other onto the wire that will be tuned for the final 40m EFHW.  I use 26ga Polysteath wire.

Step three, cut two pieces of shrink tube to cover the solder joint of the wire connectors and slide one piece of tubing on both wires.

Step four, solder the connectors onto the 30m and 40m wire sections.  When cool, slide the shrink tube onto the solder joint and shrink.

Step five, cut about 6.5” of cord and melt the ends of the cord.  Mark the center of the cord so you can center it on the connectors.  Center the cord on the connectors and slide the shrink tube over one end of the cord.  Leave the final location of the shrink tube exposed for glue.  Put a couple of drops of superglue on that area, slide the shrink tube into its final placement and shrink in place.

Step six, slide the shrink tube onto the other side of the cord and leave a little room to put glue on the cord as was done on the first end.  For strain relief on the connection, it is best to put some slack in the wire, so the full load of the antenna is placed on the cord and not on the connection.  The easiest way I have found to do this is to disconnect the connectors and overlap them by ¼” or so prior to shrinking the second shrink tube into place.  Once everything is ready, put a couple of drops of superglue on the cord, slide the tube into place and shrink.

When you reconnect the connectors, there should be a bit of slack in the wire that prevents any pull on the connectors while the antenna is deployed.  At this point restore the full original length of your antenna for add a new section of wire and tune for 40m and 20m as desired.

With K6ARK’s ingenious EFHW design and a 30m link, you can have a fantastic antenna matched to the MTR3B that is, tuned for resonance on 40m, 30m, and 20m, easy to deploy and weights under 2oz.  If you add one of Adam’s 3D printed paddles, a couple of 500mAHr LiPo batteries, and earphones your complete HF kit will be about 12oz.  Add a Carbon 6 mast and your total kit come in at a mere 23.7oz.  WINNING! 

For those operators who are fortunate enough to own an MTR4B, an 80m removable extension can be added to the 40m EFHW using a similar technique.  On the 40m EFHW, prior to installing the connector, a piece of the cordage can be folded back on itself to create a loop and slid through a piece of shrink tube.  This loop works as a good connection point for your guy lines while deploying the 40m antenna by itself and a place to tie on the 80m extension when needed.

For the 80m section, a single 5” length of cord will be connected to the wire to tie with superglue and shrink tube.  Solder the connector onto the 80m section before securing the cord.  The cord on the 80m extension is to tie the antenna sections together in a manner to provide strain relief for the couplers.  A cord loop can be put on the far end of the 80m section using this technique after it is tuned.

This is my vote for the best Mountain Topper portable easy to deploy antenna, or for any QRP radio without an ATU.  IMHO.

Antennas, New Products, News, Portable, QRP, Videos

Tiny EFHW and EFRW Kits by KM4CFT

9 Comments

Long time QRPer.com contributor and supporter, Jonathan (KM4CFT) has designed and started producing ultra-compact end-fed antenna kits (eBay affiliate link).

His end-fed antennas are incredibly small, thus perfect for portable operations. They remind me very much of K6ARK’s end-fed wire antenna kits, but a little easier to build because the board is larger and there are no surface mount components.

Jonathan sent me one of his end-fed kits (assembled) a couple weeks ago, but I’ve yet to trim mine due to my crazy schedule and activities as of late (well, that I need need to order more wire!). I will take this antenna to the field this month, but the video may not show up for a few weeks.

W2AEW Builds the KM4CFT UNUN

This morning, I learned that my good friend Alan (W2AEW) published a video where he builds, tunes and tests Jonathan’s  QRP End Fed UNUN kit:

Click here to watch on Alan’s (excellent) YouTube channel.

Alan’s video is superb. If you purchase this EFHW kit, I’d encourage you to watch his build. (And subscribe to his channel!)

How to purchase

Jonathan is selling his antenna kits on eBay–click here to check it out. The price is $29.95 plus a modest shipping fee. I think it’s an excellent deal.

Of course, you’ll need some wire for your radiator and/or counterpoise.

I plan to build mine with a 30 meter link to pair with my Mountain Topper MTR-5B.

Click here to check out the antenna kit on eBay. (note: this is an eBay partnership link that supports QRPer.com)

Click here to download the detailed assemble guide.

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

Antenna Tuners, Antennas, Homebrew, How To, News, Portable, QRP

BD4LB’s Simple Homemade L-Match for Field Operating

14 Comments

Many thanks to HUAQIANG Gu (BD4LB) who shares the following information about his homemade L-Match. Note that BD4LB doesn’t speak English, and I don’t speak Chinese, so the following was machine-translated via Google Translate:

Homemade L-Match for Field Operating

by HUAQIANG Gu (BD4LB)

L-MATCH has a simple structure and is easy to make.
It is mainly composed of a coil and an adjustable capacitor.

  1. The coil is made of copper wire with a diameter of 1.8mm, and the outer diameter of the coil is 50mm.
  2. The capacitance of the thin film adjustable capacitor is 0pF–200pF.
  3. When using, a balanced ground wire needs to be installed.
    (Different bands, multiple quarter-wave length wires, and together. I use a row of wires. For example: two balanced ground wires 10 meters and 5 meters long, respectively 40 meters band and 20 meters band balanced ground wire.)

After many outdoor communications, I adjusted the end-fed antenna. The length of the radiator was 10 meters, which was appropriate.

One end of it is hung from the top of a 6-meter-long fiberglass fishing rod. On the other end, connect the red binding post of L-match.

Balance the ground wire and connect it to the black binding post. Spread it out on the ground.

The L-match is placed on the ground and connected to the HS1B or KVE60C antenna analyzer using a one meter long 50-3 coaxial cable. (This reduces the length and weight of the coaxial cable.)
When using an inverted V antenna, the length of the coaxial cable needs to be at least 8 meters.

My outdoor communication is mainly on the top of a hill in the park, or on the beach by the sea.

On the beach, there is plenty of space. In addition to setting up end-fed antennas, you can also set up inverted V antennas.

On the top of the mountain in the park, the space is limited, and it is difficult to deploy the 20-meter-long antenna oscillator. Only 10-meter end-fed antennas can be used.

After fixing the fishing rod, installing the antenna radiator and balanced ground wire, first connect the antenna analyzer KVE60C.
Use copper alligator clips to clip on the coil and adjust the adjustable capacitance to minimize the standing wave ratio of 7.023 MHz.
(Change different coil taps, adjust the adjustable capacitor, and try several times.)

I carry a compass to adjust the transmitting direction of the end-fed antenna. I won’t get lost.

The actual communication effect is quite good.

In the 40-meter band, it is suitable for short-distance communication within 800 kilometers.

In the 20-meter band, it is suitable for communication within 1000-2000 kilometers.