Bleedover and adjacent channel rejection...
Bleedover and adjacent channel rejection...
As many have heard correctly the Cobra 200 doesn't have very good adjacent channel rejection. Is there anything that can be done to fix this? If not is there a radio on the market that is similar with great rejection?
Thanks,
DJ
Thanks,
DJ
here is all i can find
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Cobra Electronics Corporation
TECHNICAL SERVICE BULLETIN
10043
MODEL(S): 150GTL, 200GTL
DESCRIPTION: Receiver overloads when receiving a strong signal, resulting in distorted audio. In addition there may be a warble in the modulation when transmitting (which the customer might describe as a popping sound during transmit).
ACTION: RF is bleeding into the receiver front-end. Apply the following fix:
For both the 150GTL and 200GTL, install a 1µF electrolytic capacitor across C607. (From C607 to ground)
ADJUSTMENTS: None.
NOTES: None.
here's a tip for increasing receiver selectivity in the Cobra 200GTL-DX. place a 220pf cap from base to emitter (gnd) of Q-3. This allows T-701 to be peaked with the Noise Blanker ON for a 2 dB NB figure of merit. This does not affect overall sensitivity of the receiver and provides 55 - 60 dB of Adjacent Channel Rejection. Q3 is located near the top right corner of T707 on both the 150 and 200 GTL DX
Cobra Electronics Corporation
TECHNICAL SERVICE BULLETIN
10043
MODEL(S): 150GTL, 200GTL
DESCRIPTION: Receiver overloads when receiving a strong signal, resulting in distorted audio. In addition there may be a warble in the modulation when transmitting (which the customer might describe as a popping sound during transmit).
ACTION: RF is bleeding into the receiver front-end. Apply the following fix:
For both the 150GTL and 200GTL, install a 1µF electrolytic capacitor across C607. (From C607 to ground)
ADJUSTMENTS: None.
NOTES: None.
here's a tip for increasing receiver selectivity in the Cobra 200GTL-DX. place a 220pf cap from base to emitter (gnd) of Q-3. This allows T-701 to be peaked with the Noise Blanker ON for a 2 dB NB figure of merit. This does not affect overall sensitivity of the receiver and provides 55 - 60 dB of Adjacent Channel Rejection. Q3 is located near the top right corner of T707 on both the 150 and 200 GTL DX
I had a cobra 200 for a while and to get rid of Channel bleed over, it can be cured by installing a 10.695 Channel guard filter,
it will give you between 100dB to 80 dB adj channel Rejection
[ external image ]
it will give you between 100dB to 80 dB adj channel Rejection
[ external image ]