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Old 06-09-2018, 1:53 PM
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Default Stryker 94 feedback issue

I have a Stryker 94hpc in my triaxle dump truck. Occasionally I will get a little feedback through the external speaker when keying up on 10 watts, but not on 4 watts (the two AM settings the radio has). Also won't get the feedback when the external is unplugged. The radio has a Palomar MAX-MOD transistor and I am using a Wilson 500 magnetic antenna and the SWR is under 1.5. The speaker is the correct ohms. When this happens I think I am hearing talkback too but I let go of the key real quick. Any ideas why this happens?

PS I have pretty much the same setup in my Jeep except the antenna is a Sirio 5000 and no max-mod transistor, never had a problem.
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Old 06-16-2018, 12:18 PM
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Default wow

162 views and not one suggestion or request for more info.

Thanks for looking anyway.

Getting the squeal and talkback was odd in this case because neither the radio or speaker has a talkback function. And it didn't happen all the time, so it was hard to troubleshoot.

For those who may be following along hoping for an end to this madness ...

Anyway ... suggestions in other places in cyber land have helped solve the problem, ferrite chokes, lots of them.

four on the thin Wilson 500 coax right by the radio, one on the mic wire near the radio and one on the speaker near the speaker.

It was hit and miss, trying one here and there some places made it worse, I finally got fed up and used everyone I had that would fit on the coax and wallah, no more talkback or squeal, not wanting to mess with a system that was working I left the others in place.

I've never had this trouble before with other radios, using the same antenna and speakers. I can't mount an antenna permanently on the truck as I am around low trees a lot and constantly break the antenna, the magnetic mount is the only option.

Whew, hope that is the end of that.


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Old 06-16-2018, 1:27 PM
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Your picture may revel the cause of your problem. Your coax appears to be a pre-made assembly. Some of these coax lengths have very poor shielding and will "leak" RF thus causing feedback. My suggestion would be to replace the coax and connector something of better quality.
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Old 06-16-2018, 2:17 PM
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I suspect it could be related to the regulator transistor mod, but what I would do is swap radios and see if the problem follows the specific radio or the vehicle installation. Then you will have something to work with.

Edit: I typed before I read and I see you addressed the problem. Be aware that at CB frequencies, a single snap on bead does just about nothing and you need a bunch in series to have any effect. Or, you can get beads with a large enough center hole to wrap several turns around it.

Every time you double the number of turns through the bead you quadruple the inductance, so whatever a single wire passing through one bead does, two passes of wire through the same bead will give the same effect as four beads in series. This adds up rather quickly and one large bead on the antenna and one on the speaker lead with several turns will probably work much better.

Last edited by prcguy; 06-16-2018 at 2:23 PM..
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Old 06-16-2018, 3:02 PM
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Quote:
Originally Posted by rfradioconsult View Post
Your picture may revel the cause of your problem. Your coax appears to be a pre-made assembly. Some of these coax lengths have very poor shielding and will "leak" RF thus causing feedback. My suggestion would be to replace the coax and connector something of better quality.

Thanks for the reply, replacing the pre assembled coax is more than I can do, I'm a user not a tech, I did watch a video on how to do it but I have very little solder experience..
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Old 06-16-2018, 3:08 PM
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Quote:
Originally Posted by prcguy View Post
I suspect it could be related to the regulator transistor mod, but what I would do is swap radios and see if the problem follows the specific radio or the vehicle installation. Then you will have something to work with.

Edit: I typed before I read and I see you addressed the problem. Be aware that at CB frequencies, a single snap on bead does just about nothing and you need a bunch in series to have any effect. Or, you can get beads with a large enough center hole to wrap several turns around it.

Every time you double the number of turns through the bead you quadruple the inductance, so whatever a single wire passing through one bead does, two passes of wire through the same bead will give the same effect as four beads in series. This adds up rather quickly and one large bead on the antenna and one on the speaker lead with several turns will probably work much better.
For a couple of days now the beads I've added appear to have fixed the problem, no more feedback issues on transmit and no one reporting any ill sounding trassimissons on the other end. Here's to hoping it stays this way and this nonsense is finished with.
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Old 06-17-2018, 11:42 PM
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Is there a local CB shop close by? Do you know of any hams in the area? Either of those two could help you. At least the cb shop will and most hams will help if they are not bitter about CB.
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Old 06-18-2018, 7:50 AM
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I run a 56-inch Wilson 500 mag-mount antenna too. I've had great results on top of a steel-bodied car, with no such problems.

Make sure your radio chassis is grounded to help any common mode currents on the coax to get to ground. This is more important with a mag-mount antenna than one that is grounded via a physical contact with the vehicle's metal base, such as a mount situated through a drilled hole provides.

Congrats on finding what's working for you: the chokes.
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Old 06-18-2018, 2:16 PM
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Quote:
Originally Posted by FiveFilter View Post
I run a 56-inch Wilson 500 mag-mount antenna too. I've had great results on top of a steel-bodied car, with no such problems.

Make sure your radio chassis is grounded to help any common mode currents on the coax to get to ground. This is more important with a mag-mount antenna than one that is grounded via a physical contact with the vehicle's metal base, such as a mount situated through a drilled hole provides.

Congrats on finding what's working for you: the chokes.
Yes since I put all the chokes on the various cables all is good.

My problem is this is a company owned heavy highway construction tri axle dump truck, we mill and pave roads, as a result I can not avoid hitting tree branches with the antenna all the time, it even taps the silos where I get loaded with asphalt. Mounting a Wilson 2000 on the mirror can be done but gets broken a lot so I've resorted to the mag mount which give me more flexibilty.



Quote:
Originally Posted by cjflinn74 View Post
Is there a local CB shop close by? Do you know of any hams in the area? Either of those two could help you. At least the cb shop will and most hams will help if they are not bitter about CB.
No CB shops in the area I work, it's a company truck so I can't just travel to a CB shop. I do not know any hams either.

Thanks for the suggestion though.
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