I bought me a backup Cobra 25 NW ST radio off ebay. Says it deadkeys at 5 watts and swings to 25. I found that the deadkey is at 1.5 watts. Not sure about the swing; I don't have a way to test that with my wattmeter. It has echo and talkback installed. Echo on ANL switch and Talkback is on NB switch. Echo board is wrapped up in black tape inside with a knob to adjust echo. Long or short. Well anyways, I have a bit of a feedback problem. When I have the echo, talkback and ST on, it has a lot of feedback. Sounds like a bee is stuck inside the radio. (Boooooooo) is kind of like the sound it is making when I push down the mic. I have tried 3 mics, two normal cobras and a HG Noise Canceling mic. Noise mic helped some but not much. Oh the dynamike is at about half and it still makes the noise; it's worse at full. I tried this from about 6 feet away from the radio. No external speaker either. When I turn off the ST, the sound reduces but is still heard. It still does it when everything is turned off, ST, echo, talkback. I can understand the words but it sounds kind of bad. I still want to be heard loud but without the noise. Does the ST supposed to make it do that??? I thought it was only for incoming transmissions. It's a nice radio, recieves very well. Any suggestions???
Just wondering but how can I turn up the deadkey?? I like to push everything to it's max for long range talking but without adding an amp.
Many thanks!!!!!
Cobra 25 NWST help
Is the noise like a feedback squeal? If so, its probably because of a talkback. If there is a talkback it should be located across the ext. speaker jack or from the receive pin on mic jack to ground, this should be a small resistor, I would wire the resistor on a switch or use a larger resistor.
If the sound is different than a squeal and the noise can't be removed by adjusting the echo controls then check the following:
Make sure that the shielded cables from the echo board go to the ground pin on the mic jack, if not, solder them there, if they used the black wire on the echo board, clip it. I have found that if there are 2 grounds, sometimes this creates a ground loop.
Another issue that I have encountered is that on the sound tracker radios, there is sometimes compatibility issues with certain brand echo boards. Sometimes it is necessary to add a resistor from the output wire on the echo board, if this is tried, start with 5-10K Ohms.
For the deadkey, l will need to answer that question from my shop, I don't have access to that info here.
Let me know what you find.
If the sound is different than a squeal and the noise can't be removed by adjusting the echo controls then check the following:
Make sure that the shielded cables from the echo board go to the ground pin on the mic jack, if not, solder them there, if they used the black wire on the echo board, clip it. I have found that if there are 2 grounds, sometimes this creates a ground loop.
Another issue that I have encountered is that on the sound tracker radios, there is sometimes compatibility issues with certain brand echo boards. Sometimes it is necessary to add a resistor from the output wire on the echo board, if this is tried, start with 5-10K Ohms.
For the deadkey, l will need to answer that question from my shop, I don't have access to that info here.
Let me know what you find.
I have found a wire that has been cut. That is all that I find. I get a lot of squelling when I have the ST turned On. Here are some pictures of the radio.
Did you find out anything about the deadkey??
The echo board is a LT2 version.
Did you find out anything about the deadkey??
The echo board is a LT2 version.
- Attachments
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- The wire that is cut is above the first silver pot from the left. It is kind of dead center. Black wire connected to white wire.
- 100_3102.JPG (89.31 KiB) Viewed 11394 times
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- 100_3103.JPG (79.25 KiB) Viewed 11397 times
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- 100_3107.JPG (84.6 KiB) Viewed 11395 times
From looking at the pictures someone has done a swing mod. to this radio this is why you have a low carrier. To be able to raise your carrier you have to change the resistor to a higher value that is located on the solder side of the board located were JP6 used to be or you can remove the electrolytic capacitor and the resistor located at JP6 and install a jumper wire back as it was from the factory. As for the squeal or hum that you are getting in transmit check to make sure the echo board is grounded properly. Hope this helps good luck.
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ramblingman
- Technical Helper
- Posts: 331
- Joined: Sunday 21st Jan 2007, 16:35
- Location: mississippi
Thats right on timrim,Looks like from the pic. the best i can see
they are using a 100 ohm resistor on swing kit.This usually
produces about 1 watt to 1 1/2 dead key..I always use a 51 ohm
here,This will give somewhere between 2 and 2 1/2 watt deadkey.
This way you can set your swr meter cal., Also if you get that
dead key down to low, it tends to get alittle choppy on audio.
Also the relays in some amps will not even latch at 1 watt key.
Which if continued use will burn out the relay.So if you want to raise
the dead key,change that 100 ohm resistor to a 47 or 51 ohm resistor.
As far as the feedback squeal goes.It looks to me, again the best i can
tell from the pic. That the talkback is wired either to a switch making
it switchable,Or they have it going to one of the controls,Making it
variable.It has a resistor in the heatshink it looks like.So i would
guess it is probably going to one of the switchs.Anl/nb,ch 9,or either
the cb/pa switch.Probably the Anl/nb switch seeing this is the most
logical and easiest method.If it is switchable,just set your echo the way
you wanna run it.Then turn the talkback off.THis should take care of your
squeal.But if you insist on using talkback,Then cut open the heat shrink
and see what value resistor they used.I always get good results using
a 100 ohm resistor here.The talkback will be loud enough,but not
too loud causing a bunch of squealing.
they are using a 100 ohm resistor on swing kit.This usually
produces about 1 watt to 1 1/2 dead key..I always use a 51 ohm
here,This will give somewhere between 2 and 2 1/2 watt deadkey.
This way you can set your swr meter cal., Also if you get that
dead key down to low, it tends to get alittle choppy on audio.
Also the relays in some amps will not even latch at 1 watt key.
Which if continued use will burn out the relay.So if you want to raise
the dead key,change that 100 ohm resistor to a 47 or 51 ohm resistor.
As far as the feedback squeal goes.It looks to me, again the best i can
tell from the pic. That the talkback is wired either to a switch making
it switchable,Or they have it going to one of the controls,Making it
variable.It has a resistor in the heatshink it looks like.So i would
guess it is probably going to one of the switchs.Anl/nb,ch 9,or either
the cb/pa switch.Probably the Anl/nb switch seeing this is the most
logical and easiest method.If it is switchable,just set your echo the way
you wanna run it.Then turn the talkback off.THis should take care of your
squeal.But if you insist on using talkback,Then cut open the heat shrink
and see what value resistor they used.I always get good results using
a 100 ohm resistor here.The talkback will be loud enough,but not
too loud causing a bunch of squealing.
Yes, the echo and talkback are both on seperate switches. The echo is on the NB and the talkback is on the ANL. Both can be turned off and on. I would like to get a high deadkey. I do not every plan on running an amp just barefoot is what I need. Right now this radio ranges from 2 to 3 miles with a SWR of 1.0:1 with small amounts of trees. I would like to get a deadkey of at least 5 watts or higher. How can I achieve this? The echo sounds great. I love it. I think I try turning the talkback off. I am also getting some noise of the turbo on my truck. A light whining sound of the turbo. My other stock Cobra 25 did not do this and my modded 29 did not either. Is there a way to fix this without having to put an inline filter in? Many thanks!!!!!