Early 5100 RF feedback problem

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n9llo
Posts: 73
Joined: Thu Aug 01, 2002 11:23 am
Location: Indiana

Early 5100 RF feedback problem

Post by n9llo » Sat Sep 06, 2008 6:07 pm

Anyone have any clues on curing the RF feedback problem when running high power on some early 5100's. From posts here and on Batlabs this was a common problem, see the post from Steve in this thread.

http://batboard.batlabs.com/viewtopic.php?f=2&t=80036

That is exactly what my radio is doing. Any help would be appreciated. Seems to be associated with the ABC switch position. Did they revise the switch mabey? Add some shielding somewhere?

I tried to order a switch from Johnson and they blew me off.

Chris
N9LLO

n9llo
Posts: 73
Joined: Thu Aug 01, 2002 11:23 am
Location: Indiana

Re: Early 5100 RF feedback problem

Post by n9llo » Sat Sep 06, 2008 6:08 pm

I tried calling Johnson tech support and to my surprise I got a return call.
They werent any help though, a 3 year old radio with a seemingly common problem for that era and they had no knowledge they wanted to share with me about a fix.

Chris
N9LLO

n9llo
Posts: 73
Joined: Thu Aug 01, 2002 11:23 am
Location: Indiana

Re: Early 5100 RF feedback problem

Post by n9llo » Sat Sep 06, 2008 6:09 pm

Well I tried using some 3m copper shielding tape that I have. On the RF section I peeled up the clear tape that protects the mic connections and placed it on the board over the mic. Then I went all the way around the edge of the RF board. This is good stuff, conductive on the sticky side also. The problem seems to have went away. I will try to post some pictures on the board. Sure wish I knew exactly what the proper fix is though. I'm sure Johnson modified the shield or something, they are no help. BTW my 410-DA1 has Digital flash. Another reason I wonder about the RF problem, if it was upgraded to digital it must have worked at one time. I'm sure when it left the factory it worked. maybe? I guess it could be a parts built radio, I wonder if I can tell somehow?

Chris
N9LLO

n9llo
Posts: 73
Joined: Thu Aug 01, 2002 11:23 am
Location: Indiana

Re: Early 5100 RF feedback problem

Post by n9llo » Mon Sep 22, 2008 4:27 pm

OK this radio is still not 100%. Sometimes it still locks up in transmit. If anyone has any info on any design changes that cured this problem or any other potential cures feel free to chime in here. I am getting really PO'ed with this thing. I just bought one of the red VHF ones on ebay. I hope I dont end up with another POS like this UHF one, the guy has good feedback so I hope not.

Chris

WC4RAV
Posts: 42
Joined: Wed May 05, 2004 2:59 am
Location: Atlanta, GA

Re: Early 5100 RF feedback problem

Post by WC4RAV » Tue Sep 23, 2008 3:18 am

I bought a 5100 like you did from the same guy on Ebay, very clean. Looks like it wasn't used. Model is 242-5113-622-BA, firmware on bootup is 1.16.9

I have had no problems with it except the RX audio when using a speaker mike is kind of raspy..tried several Motorola mikes (NMN6191's and NMN6193's) and even a genuine EFJ (well it looks alot like an Otto) model 589-0015-057-0418 and no change. It isn't bad, just sounds like an old STX does if that makes sense. Using the speaker in the radio itself is clear, crisp and natural. It isn't enough to make me want to contact the seller, as the radio works very well on TX and RX, in fact, is one of the most sensitive portables in my cache o' radios. I am surprised at the battery life, I use the NiMH Impress batteries and go three days between charges (very little TX though). I really like these radios. According to the model number on the back, these radios are capable of P25 though I cannot access P25 programming from the keypad (have not read the radio with PCConfigure).

I also have the same UHF 5100 you have and don't have the problem. I have not opened it to see if any improvements or mods were done to it. I will check and see if anything "aftermarket" was done (e.g. foil tape, solder blobs on shield, etc).

Have you been able to open an account with EFJ? I swear I had less trouble getting a license for Astro and MTS CPS from Ma M. I merely tried to register for customer bulletins and you'd think I was applying for a job at the Secret Service.

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