KB9VBR Slim Jim GMRS Antenna versus Ed Fong DBJ-UHF GMRS Antenna

[WSBR383]

This is a non-biased review of both antennas which are both great. Nobody gave me anything for free, I bought both of them. The tests were all made on the same 70’ LMR-400 cable run, same antenna mast, same MFJ Grandmaster Meter, Mini 1300 Antenna Analyzer, BTECH UV50x3 on high power (50 w). I live in a HOA so both antennas were raised as high as could be allowed and painted (non-metal base) per HOA request.

First, I started with the Slim Jim, it is a very durable and tough little antenna, which claims a 6dB gain. It works great, I was able to reach nearly every repeater in the city, and I thought it was great on simplex GMRS frequencies too. Michael at KB9VBR was very helpful when I talked to him, and the antenna was shipped fast. What got me to consider another antenna was the high SWR’s and lower power on the repeater transmit frequencies. Overall, it is a great antenna, but although the numbers in the simplex frequencies looked great, I wanted to reach out more, so I gave Ed Fong a call.

This led me to talking with Ed Fong about some antenna theory and decided to buy the DBJ-UHF antenna tuned for GMRS, for my GMRS antenna.

I ordered the antenna and received it in two days, in the meantime, I purchased the 200 psi PVC pipe (he tells you which stuff to buy, and Lowes had it for $5 for 10’). I painted all but ½ inch on each side for the end caps to slide on.

Received the antenna, put it together, sealed with silicone at the caps, and painted the ends. First thought, it is a flimsy antenna, and the UHF connector is on a plastic end-piece, you can only finger tighten it.  This worried me and still does. 

Installed it and started my testing, and this is where it gets interesting.  Below I am having side by side forward power and swr measurements for both antennas through the GMRS band, but numbers don’t always tell the whole story, which is why I needed to write this non-biased review.

I have a buddy that lives 13 miles west as the crow flies (I am on 51^st Ave and Happy Valley and everybody knows about the mountains on 67^th Ave and 83^rd Ave) with mountains between us (not a direct line of sight for sure). With my Slim Jim, I have been able to hit the Sun City West repeater and he lives close to that so we can talk through the repeater, but I wanted to get him with simplex and with the Slim Jim, he could not hear me. Keep in mind he has a handheld, so he can’t reach me, but I wanted to reach him on simplex.

We did our first radio check, and what do you know, he can hear me 4x5 simplex, and on the repeater, he says it sounds like I am in the room.  That is the test that tells all. I know there are other things in play, but overall, I have made other radio checks and getting the same results, better transmit quality and distance and the receive side is just better.

I am attaching some images of the antenna analyzer for the antenna guys (Ed Fong Antenna Only) and also posting side by side forward power and swr’s with both antennas on the same everything (running through the MFJ Grandmaster).

Enjoy, both antennas are good and both work, but for me the Ed Fong is superior in performance, not so much durability, so for a repeater antenna that I didn’t want to mess with, the copper KB9VBR Slim Jim may be better only due to overall longevity. But for actual superior function and performance, the Ed Fong is my choice.

EDIT: I have changed the antenna analyzer images, as the original images were through a Rg8x jumper and switched to a Rg142 jumper which is a much better match throughout all the bands I have tested with my LMR-400.

 

KB9VBR Slim Jim				Ed Fong
	Fwd	SWR		Fwd	SWR
462.5500	45w	1.22		46w	1.39
462.8000	48w	1.18		45w	1.38
463.0500	50w	1.14		46w	1.39
463.3000	52w	1.12		45w	1.36
463.5500	55w	1.15		44w	1.35
463.8000	59w	1.21		44w	1.35
464.0500	58w	1.29		43w	1.35
464.3000	52w	1.37		42w	1.35
464.5500	50w	1.49		42w	1.35
464.8000	48w	1.60		41w	1.36
465.0500	42w	1.70		41w	1.35
465.3000	40w	1.80		41w	1.34
465.5500	38w	1.85		41w	1.33
465.8000	37w	1.90		41w	1.35
466.0500	34w	1.91		41w	1.33
466.3000	32w	1.91		41w	1.35
466.5500	31w	1.91		41w	1.37
466.8000	30w	1.90		40w	1.39
467.0500	30w	1.85		39w	1.41
467.3000	30w	1.80		39w	1.48
467.5500	31w	1.71		38w	1.5
467.8000	31w	1.59		38w	1.54

 

 

 

 

 

 

 

Edited June 14 by WSBR383
Changed cable better match

[kidphc]

Good review.

Not shocked by results. One antenna was designed by a Professor that teaches antenna design. The other by an amateur radio operator, whom visually reads of cue cards in his videos, not knocking him. But I would choose the antenna designed by an RF Professor with some very sound design.

The ed fong should last years, the pvc maybe not so much, depending on sunlight.

Have fun!

Sent from my SM-S901U using Tapatalk

[Socalgmrs]

Can’t stand either one of them.  Every one I know that fell for the Ed fong junk tossed them in the trash in a couple days and the other is even worse.   Just buy a good antenna.  For the money the comet 712efc blows them both completely out of the water.  Just recently we had a club member that fell for the Ed fong antenna.  He was way up on the side of a hill over looking the huge valley  with 20’ of Lmr400 hooked to a 50w base station.  He could not even break squelch on the club repeater 45miles away.  He tossed it and went with a comet712 and now he is full quieting in to the repeater and has simplex conversions all the time over 100miles away and no tuning required or needed 

[WSBR383]

WRXP381, I am sure the Comet 712 is better, but again, in an HOA, they don't allow you to have a 10.4' antenna above the roof-line.  If I had no restrictions, I would choose a different antenna.  I actually have a comet SB 790a for 2m and 70CM and love it, it was the biggest I could go and still be allowed in my HOA.

Please keep review in context, I am not saying these are the "Best" antennas, but they are the best antennas that are smaller, don't require radials, and put out decent gain for a reasonable price point.  My 13 mile reference is with mountains between btw, I can hit well over 30+ miles till I hit south mountain simplex.

As an x signal-corp officer and an electrical engineer, Dr. Fong impressed me and didn't try to sell me on his antenna, he just answered questions I had about his antenna and my locational situation.

[kidphc]

Can’t stand either one of them.  Every one I know that fell for the Ed fong junk tossed them in the trash in a couple days and the other is even worse.   Just buy a good antenna.  For the money the comet 712efc blows them both completely out of the water.  Just recently we had a club member that fell for the Ed fong antenna.  He was way up on the side of a hill over looking the huge valley  with 20’ of Lmr400 hooked to a 50w base station.  He could not even break squelch on the club repeater 45miles away.  He tossed it and went with a comet712 and now he is full quieting in to the repeater and has simplex conversions all the time over 100miles away and no tuning required or needed 

I was saying between the two, I would probably go for the ed fong. Personally, in the attic I have the x300a (hoa restrictions). Till I have the home brew 4 element gmrs yagi and the 5 element 2m yagi up.

Sent from my SM-S901U using Tapatalk

[WSBR383]

I wanted to do an update (see images on original review), I replaced the Rg8x jumper cable coming from my radio to the antenna switch with Rg142 and it helped and is better matched to the LMR-400. The images on original review are through my antenna analyzer with a new RG142 cable into the antenna switch, then 70' of LMR 400 to the Ed Fong antenna.  I will say my signal reports are really good and I am extremely happy with the end results, it is near a perfect match.  I run a Comet SB-790A antenna for 2m and 70cm on the switch as well through a 60' LMR 400 run, numbers are great on there as well.  Very happy with the set up.  Again, like I said, the Ed Fong UHF GMRS antenna just works, I have tested a bunch of different antennas and the numbers and actual field results are good.  But, just wish the UHF connector on the cap was better and/or more durable. I used some caulking to seal it up and I have it mounted to my mast with HVAC zip ties, which are hefty.

 

Edited June 14 by WSBR383
Edited original review due to cable swap

[WRQC527]

On 6/3/2024 at 6:36 PM, WSBR383 said:

WRXP381, I am sure the Comet 712 is better, but again, in an HOA, they don't allow you to have a 10.4' antenna above the roof-line.  If I had no restrictions, I would choose a different antenna.  I actually have a comet SB 790a for 2m and 70CM and love it, it was the biggest I could go and still be allowed in my HOA.

Please keep review in context, I am not saying these are the "Best" antennas, but they are the best antennas that are smaller, don't require radials, and put out decent gain for a reasonable price point.  My 13 mile reference is with mountains between btw, I can hit well over 30+ miles till I hit south mountain simplex.

As an x signal-corp officer and an electrical engineer, Dr. Fong impressed me and didn't try to sell me on his antenna, he just answered questions I had about his antenna and my locational situation.

I appreciate your taking the time and effort to test these and post the results. I've built both the copper J-pole (but not a slim-jim) and the Ed Fong for two meters. I found that the copper J-pole did better, but it was very susceptible to detuning if there was anything near it. But if you can get these things in the open, they're effective. I hear folks fairly often doing Summits On The Air on 5 watts using Ed Fongs, from 40-50 miles away. Of course, there's people here who don't like anything. 

[WSBR383]

Ya, that could have been the problem with the slim jim as well (being close to other objects), I have restrictions on antenna height.  It was a miracle that I got the HOA to approve what I have, but I had a height limit and had to submit drawings and plans for the antennas I currently have. The top of my fireplace has a metal / tin cover, so not sure if that effected my results with the slim jim or not, but it hasn't effected the Fong antenna. I am happy with the results, but don't get me wrong, I would like to have a DX-333 for tri-band (2m, 1.25m, and 70cm), plus a CA-712EFC for GMRS, but that won't happen in my neighborhood, lol, no way to hide a 10'+ antenna above the roof line.

 

73's and my advice to anyone is use what works for the situation!!

[WRQC527]

2 hours ago, WSBR383 said:

Ya, that could have been the problem with the slim jim as well (being close to other objects), I have restrictions on antenna height.  It was a miracle that I got the HOA to approve what I have, but I had a height limit and had to submit drawings and plans for the antennas I currently have. The top of my fireplace has a metal / tin cover, so not sure if that effected my results with the slim jim or not, but it hasn't effected the Fong antenna. I am happy with the results, but don't get me wrong, I would like to have a DX-333 for tri-band (2m, 1.25m, and 70cm), plus a CA-712EFC for GMRS, but that won't happen in my neighborhood, lol, no way to hide a 10'+ antenna above the roof line.

 

73's and my advice to anyone is use what works for the situation!!

I was happy to discover that my Jetstream JTM3B covers 2 meters, 70 centimeters and GMRS. It doesn't need a ground plane, so I put it on a 24 foot window washing pole.

[WSDB885]

Not to hijack the thread but I bought a N9TAX Slim Jim and have it up in my attic. It was built for the GMRS frequencies. Very happy with it. IMHO the construction is excellent also. I am a customer and nothing else.

Larry

[WSBR383]

That is awesome, truth is I posted this just to help people on my experiences.  I do believe everybody has their opinions and sometimes they try to push it on others, but I feel try things and do your research for YOUR specific situation.  Thanks for sharing your experiences it all helps people make informed decisions. 

Edited July 15 by WSBR383

[Tico]

WSBR383, The Comet CA-2X4SR with a base for a ground plane seems like it would be perfect for your situation, as it requires only one feed line and one antenna for HAM and GMRS.

 

[WSBR383]

1 hour ago, Tico said:

WSBR383, The Comet CA-2X4SR with a base for a ground plane seems like it would be perfect for your situation, as it requires only one feed line and one antenna for HAM and GMRS.

 

Tico, I have tried that antenna, it was okay and did work on 2m 70cm and GMRS, but it did not do anything really good.  I use a Comet SB-790A for 2m and 70CM and the Ed Fong GMRS for GMRS, running through an antenna switch.

 

I have been cleaning up my connectors and jumpers, impedance matching and getting the system to operate at the maximum productive (RG-142 Jumper from radio to the antenna switch really helped, was using RG-8X before), plus upgraded the connectors (Messi & Paoloni EVOlution UHF Male (PL259).  Here are results for the ED fong currently on a 70' LMR run. The results are pretty amazing.  I can reach a repeater over 80 miles away full quieting.  Repeaters that I used to have to use high power to get full quieting, I can now use medium power.  Proof is in the pudding. I am 1.1 through the GMRS band, with a 1.0 on the 465mhz.

Edited July 15 by WSBR383

[Tico]

I have Ed's Antenna for GMRS (+5db) and I am very happy with it as well, however I have 1.6 VSWR at Repeater input frequency (467.xxx). I am using 25' of LMR-400.

What mount are you using for the Comet SB-790A? how far is each antenna? 

Also, I would like to know the loss in the switch if you have already measure it. 

 

 

[WSBR383]

I am using a https://shop.mygmrs.com/products/nagoya-gpk-01-nmo-ground-plane-mount-kit for the SB-790A, the two antennas are probably 25 to 30' apart. The SB-790A states that you don't need radials, but I tested with and without and my results were slightly better with, so I keep them on.

I use a DAIWA switch DWS-CS-201A, and the loss is so minimal, I get less than 0.1db. Daiwa states 0.2db, but my loss is less. 

1.6 VSWR is acceptable in theory, but you are losing RF. Do you have your LMR-400 going directly into the radio with no other junctions or adaptors?  Are your connectors good and there is no excessive kinks in the cable?  Also, I put three ferrite beads as close to the connector attaching to the antenna on both runs of LMR-400, what is your reflected?  That could be an issue.  What meter are you using?  And have you tried an antenna analyzer?

[Tico]

I am using a nanoVNA and a Surecom SW-102. Over the weekend, I dismantled the entire system. I am currently waiting for some parts.

I will verify the readings using an Agilent Spectrum Analyzer.

My antenna was mounted on a metal pole, whereas yours appears to be on a PVC pole. This difference "might" affect resonance at the base of the antenna as well.

I will conduct further tests.

Thank you for sharing the information.

[WSBR383]

Tico, on the Fong, I am also using HVAC nylon zip ties instead of metal hose clamps or clasps as to not have any metal anywhere near it.  In my experience that does make a difference. Yes also on a PVC mast, thicker of course, and I made it adjustable for a service if necessary

 

https://www.amazon.com/gp/product/B0C61V8TCS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Edited July 15 by WSBR383

[WSBR383]

BTW, just ordered a 2nd Fong GMRS antenna for a tactical mobile repeater system. Love this antenna and it's application.  Once I get it, I will upload second real results.

[Tico]

WSBR383, I found some issues with my antenna and fixed them with the help of Dr. Ed. I am now at 1.1 VSWR. I did try the Nagoya mount you mentioned; however, the radials are very flimsy and unbalanced. With a little wind, they bounce, which affects the effectiveness of the ground plane.

 

[WSBR383]

5 hours ago, Tico said:

WSBR383, I found some issues with my antenna and fixed them with the help of Dr. Ed. I am now at 1.1 VSWR. I did try the Nagoya mount you mentioned; however, the radials are very flimsy and unbalanced. With a little wind, they bounce, which affects the effectiveness of the ground plane.

 

Excellent, can't complain about 1.1. 

[CentralFloridaGMRS]

I have both of them but moved on to a Comet CA-712EFC. I moved the Ed Fong Antenna to my other house in Gatlinburg, Tenn. It works OK. In Tennensse I have the advantage of being on the top of a mountain so I would expect the Ed Fong Antenna to work. My Comet outperforms both the Ed Fong and the KB9VBR

[WSBR383]

On 8/5/2024 at 1:50 PM, CentralFloridaGMRS said:

I have both of them but moved on to a Comet CA-712EFC. I moved the Ed Fong Antenna to my other house in Gatlinburg, Tenn. It works OK. In Tennensse I have the advantage of being on the top of a mountain so I would expect the Ed Fong Antenna to work. My Comet outperforms both the Ed Fong and the KB9VBR

Ya of course, the CA-712EFC is a 10'+ commercial grade antenna and a good one at that. Congrats, unfortunately where I live I can't have an antenna that large and/or high above the roof line.  

I have another Fong GMRS antenna on a tactical retevis repeater go box, using a 18' MFJ tripod antenna mast, works great as well.  Very light weight and movable.

[WSBR383]

I wanted to share my results of my 2nd Ed Fong GMRS antenna.  This is on a 18' MFJ tripod mast on a Retevis RT97 GMRS repeater go box, powered by a 50AH lithium battery charged by tactical solar or wall charger through SAE ports on the box.  Also using a repeaterid.com ID system with morse code.

Couldn't be more happy with the results, the machine ran all weekend and solar kept it fully charged, and hardly any battery loss over the night.  Using the 462.550 / 467.550 repeater pair with TX and RX codes.  SWR under 1.1 and getting 5.2W output after the duplexer.

The Fong GMRS antenna is the star, so lightweight and portable, with no need for grounding. Using 18' of Messi & Paoloni Ultraflex 7 with the good waterproof connectors (also have a 25' run of it if needed, love this cable and connectors for tactical or shorter runs).

If anybody has any questions regarding this set-up, I will be more than happy to help.

[WRYZ562]

On 8/14/2024 at 6:32 PM, WSBR383 said:

I wanted to share my results of my 2nd Ed Fong GMRS antenna.  This is on a 18' MFJ tripod mast on a Retevis RT97 GMRS repeater go box, powered by a 50AH lithium battery charged by tactical solar or wall charger through SAE ports on the box.  Also using a repeaterid.com ID system with morse code.

Couldn't be more happy with the results, the machine ran all weekend and solar kept it fully charged, and hardly any battery loss over the night.  Using the 462.550 / 467.550 repeater pair with TX and RX codes.  SWR under 1.1 and getting 5.2W output after the duplexer.

The Fong GMRS antenna is the star, so lightweight and portable, with no need for grounding. Using 18' of Messi & Paoloni Ultraflex 7 with the good waterproof connectors (also have a 25' run of it if needed, love this cable and connectors for tactical or shorter runs).

If anybody has any questions regarding this set-up, I will be more than happy to help.

That's amazing.  Where'd you get all the bulkhead connectors?

[WSBR383]

I got the bulkhead connectors on Amazon, bought a few different ones, and just returned the ones that didn't look as good. That is what is good about Amazon is the return process.

Thanks for the compliment.