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Ed Fong DBJ-1C J-Pole antenna kit


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#1 krvw

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Posted 25 February 2020 - 07:47 AM

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)

 

 

 



#2 axorlov

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Posted 25 February 2020 - 12:51 PM

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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- Alex


#3 axorlov

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Posted 25 February 2020 - 01:07 PM

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.


- Alex


#4 Radioguy7268

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Posted 25 February 2020 - 02:04 PM

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.



#5 Lscott

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Posted 25 February 2020 - 02:11 PM

 Squelch control on my Baofeng UV-B5 is a joke,

 

May be you can try this change:

 

http://www.miklor.co.../UV_Squelch.php

 

It's simple to do using Chirp. I changed a couple of my cheap Chinese radios and they seems to work better.



#6 SteveC7010

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Posted 25 February 2020 - 04:51 PM

Lowes carries the Schedule 20 thin wall PVC pipe. You may have Better luck asking for it this way instead of by PSI rating.

Rochester-Monroe County E911 1976 to 2003 - Dispatcher II #7010
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#7 axorlov

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Posted 25 February 2020 - 06:07 PM

May be you can try this change:

 

http://www.miklor.co.../UV_Squelch.php

 

It's simple to do using Chirp. I changed a couple of my cheap Chinese radios and they seems to work better.

Cool, thanks! I did not know that.


- Alex


#8 krvw

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Posted 03 March 2020 - 09:56 AM

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



#9 Corey

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Posted 03 March 2020 - 11:35 AM

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.

 

uhfbase2.jpg


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Just My $.02

 

Corey

 

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#10 krvw

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Posted 04 March 2020 - 08:28 AM

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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