Category Archives: Antennas

Taking the new Chelegance MC-750 vertical on a POTA activation at Lake James State Park

Back in September, I was contacted by Jesse Chen (BD7LLY) who has been a long-time reader of QRPer.com. Jesse is also the founder of Chelegance (a.k.a. JNCRadio): a company that has been producing ham radio gear and accessories since 2020.

Jesse reached out and asked if I would consider evaluating a couple of the field portable antennas he designs and produces in China.

In truth, I get a lot–and I do mean loads–of requests to evaluate products and I pass on 97% of them. I only have so much time and I simply don’t bother with gear I think is unnecessary or that could be cheaply made.

Before replying to Jesse, I did a little research on Chelegance and discovered that DX Engineering now distributes their products. I decided that if DX Engineering liked the quality well enough to add Chelegance products to their catalog, then it must be up to a decent standard. I’ve never purchased anything sub-quality from DX Engineering.

I also like the fact that Jesse is a real amateur radio operator.

After checking back in with Jesse, he decided to send me two of his portable HF antennas: the M-104 and the MC-750. In full disclosure, he sent these to me at no charge–i.e. free–with the idea I could do a proper evaluation and share my thoughts both with him and with my readers.

He knew that both of these antennas had the potential to compliment my style of portable operating. I also told Jesse not to rush ship them to me as I was quite busy. I received both antennas at the end of October.

The first antenna I wanted to try was the MC-750.

The Chelegance MC-750

When I received the parcel from Jesse, I was very impressed with the MC-750’s custom soft-sided case. The stitching and quality of it are much better than I would have expected. The interior is custom designed to hold all of the MC-750 antenna components. There’s enough extra space in it, in fact, that I can also carry a 40′ RG-316 feedline inside.

Product Photo by Chelegance

The antenna basically consists of the following components in the supplied padded bag:

  • A heavy stainless steel ground spike and matching unit
  • 40 meter coil
  • 50 cm antenna arm/extension
  • 5.2 meter telescoping whip
  • 4 yellow counterpoise wires with a wire winder board

The price for the antenna system is $250 via DX Engineering and 219€ via WIMO. Moonraker in the UK is also a Chelegance distributor, but doesn’t seem to have the MC-750 listed in their inventory at time of posting (Dec 5, 2022).

The only antenna I have that might compare with the MC-750 is the Chameleon CHA MPAS Lite which is one of my favorite portable HF antennas for its quick deployment, and overall quality. For reference, the CHA MPAS Lite retails for about $360.

I thought the best way to test the MC-750 would be to take it on a POTA activation. Continue reading Taking the new Chelegance MC-750 vertical on a POTA activation at Lake James State Park

Dave sorts out vehicle-mounted antenna SWR issues

Photo by Katie Musial.

Many thanks to Dave (K1SWL) who writes:


Comments on vehicle-mounted antennas

by Dave Benson (K1SWL)

As with Rand’s recent post about his effective vehicle setup, I and others also use a small operating table inside the vehicle.  I’ve tried a number of approaches to antennas.  Without elaborating on those schemes, I’ll note that winter is now closing in here in NH. As a result, I’m now operating exclusively from my truck. My interest is now in minimizing setup and tear-down times.  Barry (WD4MSM)

also commented about the improvement in vehicle-mounted antennas with an added ground.  I’d like to quantify that.

I’d recently ordered a number of Hustler Mobile antenna components. They’re used as a stationary-portable setup using that company’s high-quality mag-mount. As I first evaluated the antenna, I was disappointed to find the minimum SWRs to be on the high side.

These results were related to the ‘floating’ coax shield, which serves as a counterpoise with the mag-mount setup.  Worse yet, these results were inconsistent. Touching the coax connector shell at the antenna analyzer caused the SWR to jump up, as did just changing the way I held the analyzer. Bad juju! It means RF inside the vehicle, with the potential for RF-‘hot’ symptoms at the rig..  Adding a 1:1 balun inline eliminated the stray RF at the rig, but didn’t do much for the SWR. It’s also just one more gadget to bring along.

A better fix was a custom bracket that bolted to the truck frame. I first confirmed that there was low-resistance continuity between a target location and the vehicle’s cigarette lighter shell.  This was something of a ‘comedy of errors’. I had a sheet-metal angle bracket on hand and went to work enlarging a hole in it. This had the usual outcome: a drill bit grabbed the workpiece and spun it. The bracket itself was buckled beyond redemption and my finger’s now healing well.  A length of 1-1/2 inch aluminum angle bracket was just the ticket.   Note that the mounting hole needs to be offset from the coax fitting mount. This avoids an interference between the mounting bolt and coax connector shell. Ask me how I know.  The bracket assembly uses a specialty coax fitting from DX Engineering. It’s their part number DXE-UHF-FDFB.

This bracket is bolted down on one of the corners of the Tacoma’s passenger seat assemblies.  It’s the closest location to the antenna I found without drilling holes and cutting the coax.  For this vehicle, it’s a 10mm bolt and was paint-coated for appearance reasons. I replaced it with a stainless-steel bolt from a hardware store. It’s important to include a split-lockwasher between the bolt and the bracket. This’ll keep the conductivity to the frame good over time. The bracket is deburred and its corners rounded to preclude injury to passengers.

In any event, it’s out of the way of the seat’s legroom space. A 3-foot coax cable assembly brings the coax nicely up behind the rig atop the operating surface.

So- how’d it work? It’s like the difference between night and day!  The broad SWR curves vanished – replaced by typical characteristics for monoband antennas. The sensitivity to handling the coax has vanished.  (A representative curve at right.) The curves are narrower, and that’s actually a good sign- it means that unwanted resistances have been reduced. 

With this fix in place, here are the SWR minima:

Frequency    SWR

14060        1.04:1

21060        1.05:1

28060        1.16:1

I took advantage of the CQ Worldwide CW Contest this past weekend. I was able to work 101 stations on 10M, 15M and 20M with this setup.  That was from a State Park 5 minutes away.  The attraction was a large and sunny parking lot, and solar gain was such that I needed to leave the truck door open several times.  This area is kept plowed out in winter, and I may try for the POTA ‘kilo’ award from there at the 1000-contact benchmark.  

We’ll see….   73, K1SWL

Mike turns a trailer wiring harness into ready-made ground radials

Many thanks to Mike (KE8PTX) who shares the following tip:

[Recently, I walked into a] big box store and this caught my eye:

When separated, they have very little memory.

So now we have four 25 foot radials. Bonus was all were different colors. Easy to untangle.

Performance, so far, is good. Total price with clip: 12 bucks.

That’s a brilliant tip, Mike! Thank you for sharing. Like you, I’m always on the look out for products that could serve double duty in the world of amateur radio. While one can find less expensive sources of wire, for 100% copper wire pre-cut to a standard radial lengths, this is a pretty good deal!

I did some searching and pricing varies between various suppliers. 

 

Sample Retailers:

Thanks for the tip!

QRPer Notes: HA8SA’s Homebrew Transceiver, BuddiHex Review, and “Marine Mobile” in Iowa?

Because I receive so many tips from readers here on QRPer, I wanted way to share them in a concise newsletter format.  To that end, welcome to QRPer Notes, a collection of links to interesting stories and tips making waves in the world of radio!


HA8SA Stay At Home Transceiver

Many thanks to Pete (WB9FLW) who shares a link to HA8SA’s compact homebrew transceiver. As Pete notes, it’s a “very simple design but with a load of features!”

Click here to check out details on HA8SA’s website.


Buddihex review

Many thanks to John (VE3IPS) who writes:

I think the QRPers will be happy see the BuddiHex review:

https://ve3ips.wordpress.com/2022/11/10/buddipole-buddihex-deployment/

John VE3IPS


“Marine Mobile” in Iowa?

Many thanks to Rand (W7UDT) who shares this brilliant little video from K0KLB’s YouTube channel:

Had a lot of fun experimenting RMOOTA (Random Metal Objects On The Air) with the boat today.. The winds were so strong (sorry about the annoying wind/mic noise) and the noise of the engine kept us from actually driving while making QSO’s.. It was a challenge just the same being stationary in one location.

It was a big contest weekend and the QRM and Pileups were massive.. With my 5w and Random Metal Object as an antenna, it was difficult to get contacts.. I was able to catch them when they were short on business and looking for calls, lol..

We only achieved 4 QSO’s out of the 10 we wanted.. (40%) but, I’m happy with that.. I felt lucky to get one call, LOL..

Thanks for watching everyone.. We (the Skipper and Mate) hope you enjoyed watching it as much as we did making it. 73, Kevin ~ k0klb

The Lyrics written and sung by K0KLB


Many thanks to everyone for sharing their tips here on QRPer Notes!

Rich re-activates Santa Fe Prairie State Park with QRM-busting in mind

Many thanks to Rich (KQ9L) for sharing the following field report:



Field Report: Testing a horizontally-polarized antenna at a high QRM POTA site

by Rich (KQ9L)

I wanted to give a quick follow up report from Santa Fe Prairie State Park (K-7839).

As you may recall I wrote up my POTA activation from this park on Oct 23, 2022. I made 15 Q’s that day but deep down felt I could do better. The setting of the park is quite industrial and consequently the man made noise is bad. Reflecting back on this activation, I feel that the limited the number of QSO’s I made that day was due to this QRM.

I resolved to try again but this time my objective was to figure out a solution to mitigate the effects of the QRM on my QSO count. Thinking about the problem, I recalled than manmade noise typically is vertically polarized and therefore for my second attempt, I decided to test this and use a horizontal antenna.

As luck may have it, here in Chicago we continue to experiencing unseasonably warm weather and my work schedule wasn’t too busy on Thursday, November 3, 2022, so it seemed like a great chance to put my theory to the test.

For the antenna, I decided to use one which I have owned for awhile, but have never used. I had purchased a RadioWaves Double bazooka from an online retailer some time back when they were on sale and planned to set up it a flattop dipole.

If you recall from my description of the Santa Fe Prairie State Park, there is a scenic overlook which has a tree mounted pulley system perfectly spaced to mount a 20m dipole. Although this would be the first time I used the system, it turned out to be a well designed and intuitive hoisting solution to use.

The “pulley” is actually an eyelet with paracord running through the eyelet. The paracord is in a continuous loop just like rope on a flag pole. By employing a simple overhand knot I secured the end of the antenna to the paracord and hoisted the antenna up into the tree about 20ft. It literally took a few minutes and I was ready to go.

Antenna was fed with my RG-316 feedline with built in common mode choke. Since a dipole is a balanced antenna system, it really doesn’t need the choke, but it was the coax that I had packed with me and I figured it wouldn’t cause any harm or negatively affect my test. I was QRV by 3:20pm, and anxious to get on the air. Continue reading Rich re-activates Santa Fe Prairie State Park with QRM-busting in mind

Guest Post: Breaking 100 QSOs during two QRP SSB Activations

Breaking 100 QSOs during two QRP SSB Activations

by Joshua (KO4AWH)

Back in May I had to travel last minute for work to North Dakota. I typically bring radio gear in the event that I have some time to do a Parks On the Air activation. This trip presented the opportunity to activate a park in Minnesota as well as one in South Dakota. I didn’t have much time to plan these activations, but I knew I had an early enough arrival in the afternoon that I could likely activate a park in MN and then in SD. So, I picked out a park in MN close to my destination. I could go activate in MN then get over to a park in SD and activate there.

I found a nice looking State Park in MN. The idea was to activate as quickly as I could and then get back to a park in ND with enough time to activate before it got too late. K-2482 Fort Snelling State Park had 110 successful activations. That is always promising when planning out an activation. I got my rental car and headed to the park.

I also had recently purchased a HFJ-350m which is a base-loaded coil with an extendable whip. I found a tripod base I could print online and then designed an adapter so I could install a SO-239 and RG316 lead with a BNC connector. I had just tested this setup in the back yard and knew it worked, although I certainly knew it was a compromised antenna.

HFJ-350m setup on custom tripod in the backyard for testing
Custom 3D Printed Tripod with BNC Connector

I typically bring my Raspberry PI4 loaded with Build-A-Pi and then run digital modes from my phone or Tablet. My plan was to activate this park with the compromised antenna running 5W on FT8 at the first park and then go to my second park and run a full half wave wire in a tree on SSB at 10W.

Not much to say about the activation in MN. The state park was nice but where I set up presented quite a bit of RF noise. Not so much of a problem since I was running digital. After a bit of adjustment on the whip I was tuned for 20m and started hunting a few FT8 stations. I did make a few QSOs while hunting but I then started calling CQ and had a bit more luck. I think because my signal was quite weak, calling CQ was a bit more efficient as only those who could hear me were calling back. While hunting, if those calling CQ were running a bit more power, I was unlikely to get in while running lower power and on a compromised antenna. I got the activation completed with 12 QSOs and packed it up and headed to the next park.

Continue reading Guest Post: Breaking 100 QSOs during two QRP SSB Activations

POTA with the Icom IC-703 Plus: Working a serious SWR problem first, though!

If you’ve been here long, you’ve no doubt noticed that I have a sizable collection of QRP radios I take to the field.

Although I have some favorites, I try to rotate all of my radios in the field and even pair them with different antenna combinations as much as possible. If I only owned one field radio, I’d shake things up by pairing my one radio with different antennas deployed different ways during my POTA/SOTA activations.

I get a real thrill out of testing different combinations, actually, and I feel like it keeps me on my toes because I don’t get too comfortable with any one setup in the field.

No doubt, using a wide variety of radios gives me a more informed perspective when beta testing or evaluating new radio models.

That said, there is one radio in my collection that has been overlooked too many times: my Icom IC-703 Plus.

Many of you have noticed this, in fact.  I’ve gotten several emails and comments asking, “So Thomas…when are you taking the 703 out again–?” 🙂

When I purchased the ‘703 from my buddy Don a couple years ago, I imagined taking it to the field very regularly. I always thought it was a cool little radio and with its built-in ATU, it’s quite compact for a tabletop-style rig.

Thing is, each time I’ve taken it to the field, I’ve had issues with the electronic keying that I did not have when using it in the shack. It’s quite sensitive to RF, so end-fed antennas seem to create unwanted dits and dashes in the keyer.

The simple fix, I hoped, was simply using an in-line common mode choke to keep the RF away from the radio. Thing is, the IC-703 has an SO-239 antenna port and two of my common mode chokes are BNC. I meant to purchase a BNC-to-PL-259 adapter at the Shelby Hamfest, but picked up the wrong item (I should have been wearing my glasses).

Then I remembered that my Chameleon 50′ RG-58C/U cable not only has an integrated in-line choke, but also PL-259 connectors. This could work! Continue reading POTA with the Icom IC-703 Plus: Working a serious SWR problem first, though!

Sam builds a tiny tabletop HF antenna

Many thanks to Sam Duwe (WN5C) who shares the following guest post:


A (surprisingly good) tabletop HF antenna

by Sam Duwe, WN5C

I recently built a tabletop QRP HF antenna for 17 and 20 meters, in the spirit of the Elecraft AX-1, so I could operate at lunchtime on the campus where I teach. My wants were something small, that would fit in my work bag, that didn’t require a tuner, and could work on a couple of different bands. But on a lark I decided to attempt a POTA activation at Lake Thunderbird State Park (K-2792) pairing this antenna with my Penntek TR-35 QRP CW transceiver. I figured I’d maybe get one or two QSOs and then switch to a long wire in a tree. But what happened amazed me.

I talked to seemingly everyone. Beginning at 9:00 AM September 26th I worked both 17 and 20 meters for an hour and a half and made 37 contacts from across the country. I even had a Swiss guy call me back on 17 but he faded before we could finish. This antenna, at least as a CW POTA activator, works. Granted conditions were very good, but I’ve replicated this multiple times in the past few weeks, just recently at a picnic table in the parking lot of the Route 66 Museum (K-8644) in Clinton, OK (there is quite a thrill in urban activations).

It has also reasonably low profile and very quick to setup and take down. It is also quite a conversation piece when I set it up at school. I elevated the counterpoise by attaching it to a nearby oak and an interested undergrad sheepishly asked if I was listening to the tree!

The build is pretty simple. Physically the antenna consists of a small painters pole from Walmart and an old tabletop camera tripod. I found a nut that fit the screw portion of the tripod and hot glued it into the orange connecting section of the pole. That way the tripod can then be screwed onto the pole. The RF parts of the antenna consist of a 38” telescoping whip that I scavenged from the rabbit ears antenna that came with my RTL-SDR. It connects using the original connector which was hot-glued into a hole I drilled into the top of the painters pole. I found similar small 3 or 4-foot whips from AliExpress for cheap and these would probably work fine.

I then soldered a long length of speaker wire that was wound into two coils: the top for 17 meters (24 turns) and the bottom for 20 meters (25 turns plus the former 24-turn coil). The speaker wire was the soldered to the center of a BNC connector which I hot glued and taped to the pole. I soldered a short piece of wire from the shield of the BNC for the counterpoise and added an automotive spade connector to attach to a 17-foot length of wire. I also included a switch between the coils and the BNC connector to select either just the top coil (17 meters) or both coils (20 meters) using solder, hot glue, and tape.  I then covered my shame in silicone tape.

The most time-consuming aspect of the project was tuning the antenna. It required trial and error to first tune the number of turns on the 17-meter coil and then the 20-meters coil. I extended the counterpoise (for me it’s best when slightly elevated) and the telescoping whip. I performed the tuning with the whip not fully extended to give room to tune in the field. Using a nanoVNA was useful here, as was soldering a pin to the wire to poke through the wire at various parts of the coil to find the best SWR.

In use, the antenna can be affected by both body capacitance and how the counterpoise is situated, so I found that an in-line SWR meter was helpful in making sure all was well. Once set up it is easy to fine tune by just adjusting the whip length. 1.5:1 SWR is about how well I can tune on average. Obviously if you have a tuner you would just have to get it close.

There are a million variation on a small base-loaded vertical antenna, and you can definitely improve upon this design. And, besides the super well-built and elegant AX-1, QRP Guys sells an interesting looking kit, and there are some good 3D printed designs I might want to try out. But regardless how you go about it, it might be worth giving a tiny antenna a shot.

72, Sam WN5C

Jonathan demonstrates using a K7QO noise bridge and shares a 3D printed OM0ET loop mount

Many thanks to Jonathan (KN6LFB) who shares the following in reply to my recent post about tuning mag loop antennas:

Hi Thomas,

I made a short video showing the use of a K7QO noise bridge from QRPguys to tune a mag loop antenna:

Also, inspired by your post, I dragged my OM0ET magloop up a mountain today for a POTA activation. I used a 3D printed tripod adapter of my own design that allows me to mount it on the collapsing legs from the Buddistick Pro. It makes the whole package a lot more manageable and light weight than carrying a camera tripod.

I had a successful activation of K-4454 on 20 meters, and thought you might enjoy some photos of the setup:

I’ve uploaded the design to Thingiverse at this address:

https://www.thingiverse.com/thing:5589250

73,
Jonathan KN6LFB

Wow! Thank you Jonathan. That short demonstration prompted me to order the K7QO noise bridge kit from QRPguys this morning. In fact, I plan to build this and keep it with my loop antenna as it’ll pair so nicely with my IC-705 and TX-500!

Thank you, also, for sharing those 3D files! I love that field setup at K-4454!

Honing my mag loop tuning skills

Yesterday, I posted the photo above on Twitter.

I couldn’t help it: I’m not an “Instagram Moment” kind of guy, but the fall leaf colors this year have simply been stellar. Any excuse.

Where was I? Oh yes…

Truth is, I was in the front yard practicing my loop tuning skills by hunting parks across 30, 20, and 17 meters.

The loop is the excellent Chameleon F-Loop 2.0 (which has since been replaced by Chameleon with the 3.0 version).

I’ve used this loop a few times in the field and even once from inside a large brick community building while doing an FT8 demo.

Loops are a brilliant solution when you have:

  • QRM from local noise sources,
  • limited space to deploy an antenna,
  •  or need a very low-impact and small footprint antenna (very handy for those historic and archeological POTA sites).

The trade-off, of course, is that they have a high “Q”–meaning very, very narrow bandwidth. Basically, anytime you move frequency? Yeah, it’s time to re-tune.

The environment around a loop can also have a pretty significant impact on your ability to tune it as well. For example, metal support structure in a building, window frames, metal poles, vehicles–anything like this nearby can have an impact on your ability to tune a loop and obtain a low SWR.

It’s for this reason I use them so little in the field–where I live, wire antennas are so easy to deploy and use.

But sometimes loops are the perfect tool, so knowing how to efficiently and effectively use them is important.

The F-Loop packed

I thought I had posted an activation video using the F-Loop, but looking back I realize I have not.

Yesterday, I decided to pack the F-Loop in my larger Spec-Ops Brand T.H.E. Pack which can easily hold the entire loop, folding tripod, and antenna analyzer.

I always fully set up an antenna before packing it in a new pack just to make sure I’ve included all components.  I used this as an excuse to improve my loop tuning skills by intentionally chasing POTA stations across the HF bands. I worked all of the stations I hunted (five, if memory serves).

Twice I obtained a brilliant match just by using my ear (listening for the HF band noise level to increase as I tuned the variable cap) and the rest of the time I turned to my RigExpert handheld analyzer to find a low SWR.

I’m looking forward to taking the F-Loop to the field soon just to see how well it performs. After my practice today, I do believe I’ll keep the antenna analyzer packed with the loop–it makes it so easy to find a good match.

I find the F-Loop a wee bit easier to tune than my W4OP loop. The W4OP loop is also a brilliant loop if you can find one–I recently gifted mine to a friend. Here’s my review from a few years ago.

I’ve used an AlexLoop once and was impressed as well. That’s another antenna I may review at some point.

Commercially-produced mag loops are pretty expensive though. I do plan to build a 20M mag loop antenna before end of year.  They’re surprisingly easy to build if you have a good variable cap.

Curious how many of you regularly use mag loop antennas. If you do, what make and model? Or is your loop homebrewed? Please comment!