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Ed Fong DBJ-1C J-Pole antenna kit


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Still very preliminary to draw my final conclusions, but I received my Ed Fong DBJ-1C antenna kit and an antenna analyzer this weekend (on the same day I passed my ham tech exam, so that was fun).

 

I ran a couple of antenna placement tests quickly. My aim was to communicate with my wife in her office, first via the local Alexandria GMRS repeater and then see if I can achieve simplex to her (2.1 miles).

 

The good:

 

- Deployed at attic height, my wife reports my voice is the clearest she has heard it over GMRS. All good.

 

The bad

 

- Still no simplex comms. Not even breaking squelch. I'll keep trying, and will work on a mobile at home as well. I can still go higher on the antenna and mount it roof top, but that requires HOA permission and a whole lot of hassle. Still, I may well do that soon.

 

The surprising:

 

- Antenna analyzer (SureCom SW-33) in hand, I measured everything. I have the ducky that came with my handheld as well as a Nagoya NA-771 and a Nagoya NA-701C. I also have a Nagoya UT-72 mobile mag mount, but have not measured that one yet. All the duckies suck, at least in terms of SWR on the GMRS freqs I use the most. Lowest SWR I measured was 2.0; highest was 4.5.

 

- The Ed Fong DBJ-1C, on the other hand, measured in 3 separate measurements, a paltry 1.02. That seems nigh on perfect, and may well explain the clear and strong signal my wife received from me.

 

I've heard some good and bad things about the Fong kits. (Calling them kits is even a stretch. All you do is insert it in a 5 foot PVC 200 PSI pipe and you're done. Toughest part is finding 200 PSI and not the ubiquitous "Schedule 40" (480 PSI) piping.)

 

My initial impressions are that the nay sayers are largely wrong, at least compared to my needs and deployment. Oh, I should add that I used a high quality LMR-400 feed line with PL-259 connectors.

 

(Aside: As I operate mostly in UHF, is it worth changing from PL-259 to BNC, N, or some other connector better suited for these freqs?)

 

Cheers,

 

Ken

WRFC318

(ham sign pending FCC)

 

 

 

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I have SureCom SW-33 and I have Diamond SX600. While they mostly in agreement when measuring power and SWR on 2m, they wildly disagree on 70cm and GMRS. I decided to trust Diamond. Surecom measurements are inconsistent even with dummy load. Another thing to consider is that measuring SWR with HT and HT antenna is a tough proposition. HT antennas are designed to work when you hold HT in hand and your body is capacitively coupled with it. Surecom "stick" is comparable to 1/8 wavelength on GMRS and it will change antenna characteristics when inserted between HT and antenna. Same with using pigtails. I do not bother measuring SWR on HT antennas because of that. Measurement equipment introduces a systematic error that is big enough that you can't trust the measurement, Surecom or not.

 

Measuring SWR of Fong antenna or mag mount antenna is a different exercise. In case you're measuring at antenna base, you will get correct SWR of the antenna. In case you're measuring at transmitter, the loss in the cable will lower SWR, the bigger the loss the closer your SWR to 1:1. Do not obsess with SWR, better measure the power at antenna base. SWR does not directly affect efficiency of the antenna, it is indirect metric of the loss in your transmission line and (very) indirect hint at if transmitter will reduce power or burn out.

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2 miles do not sound like too damn far. My next steps would be:

1. put one operator at home and another operator in car or on foot, and start walking away, find places when 100% availability becomes 75%, 50% and none;

2. borrow HT with better selectivity from your ham friends and see if reception improves at places you identified in step 1.

 

Wide open front end on Baofengs cause de-sense in places with a lot of RF, like downtowns, offices, next to computers, etc. Squelch control on my Baofeng UV-B5 is a joke, program one of the buttons to disable squelch and use it during your experiments. You should use it anyway - to monitor the frequency before transmitting.

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Type N connectors are preferred. I forget where the exact drop-off point is for the SO-239/PL-259 "UHF" connector - but the term is borrowed from WWII era when anything over 50 MHz was considered an "Ultra High" frequency.  Even using the PL259 in VHF is a stretch. People assume that since they're usually called "UHF Connectors"  - you should be good to go using them for UHF frequencies.  Use Type N when you can.

 

That said, if you've already got them, and they're installed, they're probably not killing you. Don't use an adapter just to get to a Type N fitting. You won't gain anything.

 

Your biggest issue is the type of radios that you're using. Get away from those "radio on a chip" CCRs - and pick up something with an engineered front end that is designed to pick a weak signal out of the weeds at a specific frequency. I'll always tell someone to look for used Kenwood, Motorola, or even Vertex over any of the cheap Baofeng or BTech variants.

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Follow-up here for anyone interested...

 

Since I live in an HOA, I don't want to apply for an outdoor antenna until I'm certain. That is, I want to continue some indoor tests first.

 

I now have both my GMRS (WRFC318) and ham (KO4CGK) licenses, and have the Ed Fong j-pole in both freqs. Hoping to have a deployment that makes it quick and easy to switch between the two.

 

For now, I have them in my attic space, as high up inside the house as I can go. (I estimate 25 feet above ground level.)

 

I want a mount that isn't permanent and enables me to swap antennae quickly. Here's what I came up with.

 

3" PVC end hot glued at high end

Swiveling "broom stick" mount holding the low end in place.

 

$3 at Home Depot. I can swap antennae in about 10 seconds.

 

My hope is to get one of them mounted on the roof during the Spring or Summer.

 

Cheers,

 

Ken

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I tried an Ed Fong j-pole in the attic 6 years ago and it went in the trash 10 min later, worthless as far as resonant, basically a nice dummy load. Several years ago I purchased an Andrew DB404 for my base, still 30' in the attic but I am able to hit my repeaters 35 miles away. I regularly talk simplex 25 miles without an issues. As with anything, you get what you pay for.

 

http://mwgmrs.com/mygmrs/uhfbase2.jpg

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I tried an Ed Fong j-pole in the attic 6 years ago and it went in the trash 10 min later, worthless as far as resonant, basically a nice dummy load. 

 

Wow, my own experiences have been the polar opposite of that. I have the GMRS version and then bought the ham one when I passed my ham tech (KO4CGK) a couple weeks ago.

 

In both cases, the local repeaters I frequent are barely reachable on my handheld, forcing me to go outside to speak on them. But with the respective Fong in place, I'm reaching them 5x5. Distances are in the 9-10 mile range, and the radio checks I've performed told me my voice is coming through crystal clear.

 

I have no idea what went wrong for you, but "dummy load" couldn't be further from what I experienced. Perhaps you used thicker Schedule 40 (480 PSI) PVC tubing instead of the thinner Class 200 stuff that Fong recommends?

 

Working great for me.

 

Cheers,

 

Ken

WRFC318

KO4CGK

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  • 9 months later...
  • 4 weeks later...

Still very preliminary to draw my final conclusions, but I received my Ed Fong DBJ-1C antenna kit and an antenna analyzer this weekend (on the same day I passed my ham tech exam, so that was fun).

 

I ran a couple of antenna placement tests quickly. My aim was to communicate with my wife in her office, first via the local Alexandria GMRS repeater and then see if I can achieve simplex to her (2.1 miles).

 

The good:

 

- Deployed at attic height, my wife reports my voice is the clearest she has heard it over GMRS. All good.

 

The bad

 

- Still no simplex comms. Not even breaking squelch. I'll keep trying, and will work on a mobile at home as well. I can still go higher on the antenna and mount it roof top, but that requires HOA permission and a whole lot of hassle. Still, I may well do that soon.

 

The surprising:

 

- Antenna analyzer (SureCom SW-33) in hand, I measured everything. I have the ducky that came with my handheld as well as a Nagoya NA-771 and a Nagoya NA-701C. I also have a Nagoya UT-72 mobile mag mount, but have not measured that one yet. All the duckies suck, at least in terms of SWR on the GMRS freqs I use the most. Lowest SWR I measured was 2.0; highest was 4.5.

 

- The Ed Fong DBJ-1C, on the other hand, measured in 3 separate measurements, a paltry 1.02. That seems nigh on perfect, and may well explain the clear and strong signal my wife received from me.

 

I've heard some good and bad things about the Fong kits. (Calling them kits is even a stretch. All you do is insert it in a 5 foot PVC 200 PSI pipe and you're done. Toughest part is finding 200 PSI and not the ubiquitous "Schedule 40" (480 PSI) piping.)

 

My initial impressions are that the nay sayers are largely wrong, at least compared to my needs and deployment. Oh, I should add that I used a high quality LMR-400 feed line with PL-259 connectors.

 

(Aside: As I operate mostly in UHF, is it worth changing from PL-259 to BNC, N, or some other connector better suited for these freqs?)

 

Cheers,

 

Ken

WRFC318

(ham sign pending FCC)

 

I have bought Ed Fong's antennas.   For GMRS I purchased the DBJ UHF antenna.  It is only 3.5 feet inside the pvc tube.  Before this I was using a copper j-pole tuned for UHF and it did ok.  The mast was up at 15 feet.  With the j-pole I could get out 3-5 miles tops.  Simplex.  When I got Ed's antenna kit in, I got it together and pushed up the mast more. It sits at 28 feet now. My simplex test was out 10 miles to the North where the most buildings and trees are at.   The repeaters went from 2 S-bar readings and now getting full S-bars on the radio.  All but one of the repeaters is quieting.  I hear everyone most clearly.  

 

So far, and it's only been a week up now, I have been surprised and happy with it.  The SWR is spot on at 1:02 and at the other end, 1:07.  

 

I also have and tried to use as a base antenna, the Nagoya NMO-200C.  As much as I would tune this antenna, with the ground plane kit, I could not get it to work.   I put it on my car and it works fantastic though.  That's why I got Ed's antenna.  

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I would trust Corey's advice on this one over most others. He has setup repeaters with ranges exceeding 30+ mile range, and I listen to his repeater (Madison 700) all day long...  so, I think he knows what he is doing.

 

Yes, I would ditch all UHF connectors while at it.

 

G.

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I honestly do not understand fascination with Ed Fong's J-pole. It's clever design, true. It's easy to build yourself if you know how to measure velocity factor of the coax and twin-lead and have tools to do so. But in the form Fong sells it, it lacks important feature: common mode choke. J-pole design is very susceptible for common mode current on the outside of the coax, it's inherent in the design. When you add suitable choke (and do a lot of research if you a newbie), add PVC and mounting hardware, your total cost is about $80.

 

For GMRS forget Fong's antenna and buy yourself a nice Browning BR-6140. It is unity gain (like Fong's dual band), it has RF choke integrated (unlike Fong's), has N connector (unlike Fong's), has mounting hardware included (unlike Fong's). It's plug-and-play and fool-proof (totally not like Fong's). It's about 24" length (Fong's is 5 feet). What not to like? It's $36 on Newegg! Go buy two, for yourself and your aunt.

 

And if you're Ham, options are plenty. For example, Diamond X50. It's dual-band (like Fong's), 5 feet long (like Fong's), it's 4 or 5dBi on 2m and 7dBi on 70cm (unlike Fong's), has common mode choke, N connector (X50NA variation) and mounting hardware. It's also plug-and-play. Available at different places for roughly $100. Yes, it's not tuned for GMRS. You will get perfect SWR on ham bands and 1:1.7 on GMRS. So what? Fong's antenna will give you any SWR from 1 to infinity depending on where wind blows from, and alignment of the stars on particular night.

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I don't know all.  It seems to be working fine for me.  It's what I have up right now and SWR is good so it is staying for a while.  Maybe some point down the road I'll invest in something else but if it works for some then it's like anything else in radio, use what works for you.  Sometimes you need to experiment and learn.  I've gotten some good antennas in the past 15 years and some of those that were supposed to be good. After install and tuning, they ended up being garbage too.  I think how one antenna works for one person may be different for another's set up.  

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I don't know all.  It seems to be working fine for me.  It's what I have up right now and SWR is good so it is staying for a while.  Maybe some point down the road I'll invest in something else but if it works for some then it's like anything else in radio, use what works for you.  Sometimes you need to experiment and learn.  I've gotten some good antennas in the past 15 years and some of those that were supposed to be good. After install and tuning, they ended up being garbage too.  I think how one antenna works for one person may be different for another's set up.  

 

I'm confused.  The antenna was tuned and was garbage?

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I'm confused.  The antenna was tuned and was garbage?

 

Guess you had to be in my brain..  It means that after trying to tune the antenna it still did not work. Tried my best to tune it so yea, it was tuned in a sense, perhaps not what you are used to hearing!  And it ended up garbage for my use.  

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