Pro-106 Antenna Repair

N3FAH · #1 (**permalink**) 11-19-2012, 3:18 PM

WARNING: This post contains graphic descriptions and images of the internal organs of a radio that are not suitable for the faint-of-heart. :-)

Recently my Pro-106 lost sensitivity (again), at first It lost just digital, but the longer I listened, the more stations dropped out. Finally I could hear only very strong and/or very close stations. After a week of agony thinking it was toast, I decided to open the box and have a look. (This is where the squeamish should tune out.) The main logic board is on top, it contains the RF and IF sections, the scan logic, etc. And the antenna jack - the BNC connector, mounts here. The RF section is shielded in a steel "can", but there are a couple of holes that you can peek through. If you peek in with a flashlight, you can see where the center pin of the BNC comes out on the chassis end. There is a little 1/8" loop of wire that comes up from the PC board and makes a half-turn around the BNC pin and is soldered there.

Given enough antenna swaps, the center conductor of the BNC will work back and forth until the solder joint breaks. That's when the sensitivity starts to decline. Hey... if the signal can make it thirty miles from the transmitter to the antenna, you'd think it could jump one more little 1/64" gap, wouldn't you? You'd be wrong. (Sorry, don't take it personally.) With the back cover off, and the radio on house power and scanning, use a thin NON-CONDUCTIVE plastic probe to -very gently- poke through the top gap on the inboard side of the shield 'til you can touch the wire from the PC board to the BNC - if the wire moves, and the signal strength improves -dramatically- you have found your culprit. (look for the attached photo.)

You'll have to re-solder that connection. With all POWER REMOVED, CAREFULLY peel up the top outboard corner of the shield. I snipped back the shield a little more to get my solder iron in there. Slide a strip of thin cardboard or heavy paper under the joint to protect the circuit board from "oopsies" and re-solder the antenna wire to the BNC. Remove the paper, blow out the 'can' to remove any debris. Bend the shield gently back in place being careful not to short anything, reassemble and you're done.

This is the second time I have had to do this. Analog FM signals are very forgiving - there are strong stations, and weak stations, but you can (usually) hear what's being said. Digital signals, on the other have, are essentially "all or nothing". If you don''t have a strong enough signal, either it "pixellates" and breaks the signal into undecipherable 1s and 0s; or the radio doesn't even see the signal at all. And if you swap the radio like I do from rooftop antenna to rubber ducky to car antenna... well, there goes the BNC. (OK, I hear ya, I brought it on myself. But hey, I fixed it too. And one "attaboy" wipes out a bunch of "aw $&#@s", right?)

Anyway, sorry for the lloonngg post but gotta get it all in one place. Good luck. N3FAH

tonyclark · #2 (**permalink**) 11-19-2012, 4:01 PM

DAMN! that's graphic. Scanner inards everywhere.

n5ims · #3 (**permalink**) 11-19-2012, 5:05 PM

Something like this (BNC Male to BNC Female Adapter) may prevent (or at least delay) your need to do the repair for a third time. The disconnect-connect stress should be on the adapter, not the scanner so when things wear out, you only should need to replace the adapter.

gr8rcall · #4 (**permalink**) 11-20-2012, 8:29 AM

Quote:

Originally Posted by n5ims

Something like this (BNC Male to BNC Female Adapter) may prevent (or at least delay) your need to do the repair for a third time. The disconnect-connect stress should be on the adapter, not the scanner so when things wear out, you only should need to replace the adapter.

I'm gonna get one of those! As I'm not looking forward to having to do surgery on my scanner....

ashgoon · #5 (**permalink**) 01-11-2013, 8:52 PM

Maybe I missed something. (Pobably) What is the purpose of the "steel can" over the BNC connector to the PC board? How far bac can it be cut to re-solder the BNC conection? Been fighting thesame problem on my106 as well. Thanks.

jaspence · #6 (**permalink**) 01-11-2013, 9:13 PM

Using the adapter may help, but if you use any longer antenna or a long piece of coax, it will have the opposite effect because of the extra stress it puts on the original connector. The only way it will really help is if you remember to hold it when you remove and replace the antenna. If you just grab the antenna, the stress still ends up on the original connector. If you are using an antenna with coax, there are adapter cables a foot or two long that have very thin coax to connect to the regular coax. I have a collection of over thirty handhelds (ham and scanners), and I use this type whenever I want to us a regular antenna.

DickH · #7 (**permalink**) 01-12-2013, 3:32 AM

Excellent presentation Richard. It's good to see a real Ham on here, although I see you used to be a semi-Ham.

ampulman · #8 (**permalink**) 01-12-2013, 6:22 AM

Quote:

Originally Posted by jaspence

...Using the adapter may help, but if you use any longer antenna or a long piece of coax, it will have the opposite effect because of the extra stress it puts on the original connector. The only way it will really help is if you remember to hold it when you remove and replace the antenna.

I wondered about this with my 396T. I use the GRE 800 antenna by RS with the adapter. For a long time, I would just unscrew the antenna with no problem. After a time, the adapter started to rotate with the antenna. I have found that by pressing downward on the antenna before rotating, the adapter stays put.

It also works with (flexible) coax. I did, however, support the coax when the scanner was in position (at home), so that no strain was placed on the adapter.

Amp

Ensnared · #9 (**permalink**) 01-12-2013, 11:44 AM

Quote:

Originally Posted by n5ims

Something like this (BNC Male to BNC Female Adapter) may prevent (or at least delay) your need to do the repair for a third time. The disconnect-connect stress should be on the adapter, not the scanner so when things wear out, you only should need to replace the adapter.

There are numerous posts about this issue. When I was visiting Iowa, I let a buffoon fix my scanner antenna. Instead of asking if he could install a PL-259, he did it without my permission. This resulted in having to use a BNC adapter. In my opinion, the extra metal above the scanner created a fulcrum effect on the BNC housing. Within three weeks of installing this setup, I was sending my radio back to GRE for repair. I don't recommend using adapters for this radio. If you are extremely careful to avoid hitting the extra metal, you might get lucky, but I don't recommend this setup.

fourthhorseman · #10 (**permalink**) 01-12-2013, 12:24 PM

Had to make the same repair on my 106..BNC was hairline cracked..so i just cut back the sheilding
and replaces with a short length of coax..

removing the shielding is not the best way,,but it works no the less...

gewecke · #11 (**permalink**) 01-12-2013, 7:12 PM

Quote:

Originally Posted by ashgoon

Maybe I missed something. (Pobably) What is the purpose of the "steel can" over the BNC connector to the PC board? How far bac can it be cut to re-solder the BNC conection? Been fighting thesame problem on my106 as well. Thanks.

DO NOT cut the shielding in place over the bnc! Remove it with a desoldering station then solder a 1/2" piece of braid to the center pin and the pcb. re-solder the shield AFTER replacing the bnc with a amphenol bnc. Loctite the nut on the bottom of the new bnc. The whole process takes about 1 hour, assuming your bench is well equipped and your soldering skills are proficient!
I've done this once on my own pro-106 and one other one for a customer, and this is the best option,aside from sending it to GRE for repair.

73,
n9zas