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Cobra 2000 low recieve
- Thread starter BAGEBOY
- Start date
Of the two top causes of this, the first will be alignment. If someone starts turning every tuning slug he sees one after the other with the mike keyed, he'll be watching the wattmeter for even the smallest upward twitch of the needle as he twists each slug.
This is a good way for multiple receiver adjustments to be thrown totally out of whack.
Starting with a signal that's just audible, each receiver slug gets peaked for max signal.
If you don't have a handy source of a steady receiver signal, this is a handicap.
And if any of the skinny slugs appear to peak with the top of the slug DEAD EVEN with the rim of the hole, this is the second most-common cause. A deteriorated capacitor inside that 'can'. A legitimate peak will occur with the top of the slug at least two turns below that rim.
But you have to attempt alignment just to catch this failure.
73
This is a good way for multiple receiver adjustments to be thrown totally out of whack.
Starting with a signal that's just audible, each receiver slug gets peaked for max signal.
If you don't have a handy source of a steady receiver signal, this is a handicap.
And if any of the skinny slugs appear to peak with the top of the slug DEAD EVEN with the rim of the hole, this is the second most-common cause. A deteriorated capacitor inside that 'can'. A legitimate peak will occur with the top of the slug at least two turns below that rim.
But you have to attempt alignment just to catch this failure.
73
What I realise I keyed my radio and it was on and it went to 30db...so strong signals seem to be coming in with very little signals..so I went on channel 6 I could hear the strong stations butsmall.signals then it goes quiet ..no static noise nothing when I check the other radio skip is 9db ..so I dont know if this post makes it clearer tonight my static is like 3 dBon my rafio when I check the radio 0 and no noise etc
Seems pretty clear-cut.
You have a receiver that has lost its sensitivity.
Hears a strong signal. Can't hear a weak one.
If it were properly sensitive it would hear a noise level.
This is a familiar symptom. The most-common causes listed above are what we check first.
73
You have a receiver that has lost its sensitivity.
Hears a strong signal. Can't hear a weak one.
If it were properly sensitive it would hear a noise level.
This is a familiar symptom. The most-common causes listed above are what we check first.
73
L12 and L14 are the two SSB-only IF transformers in the radio. These each have the small ferrite tuning slug, not the large ones with the fat screwdriver slot.
Requires a non-metal tool about 1.3 mm wide to turn them. A tool with a metallic tip tends to disrupt the adjustment.
You'll need a steady signal that only pushes the S-meter up to a 1 or 2, max to see a proper peak response when turning these tuning slugs.
If either or both of these is not peaked, this will reduce sideband sensitivity without affecting AM.
And if the receive signal peaks with the slug DEAD EVEN flush with the rim of the hole, that's a bad sign.
That's where I would look first for a sideband-only receiver problem, in the two adjustments that affect only sideband.
73
Requires a non-metal tool about 1.3 mm wide to turn them. A tool with a metallic tip tends to disrupt the adjustment.
You'll need a steady signal that only pushes the S-meter up to a 1 or 2, max to see a proper peak response when turning these tuning slugs.
If either or both of these is not peaked, this will reduce sideband sensitivity without affecting AM.
And if the receive signal peaks with the slug DEAD EVEN flush with the rim of the hole, that's a bad sign.
That's where I would look first for a sideband-only receiver problem, in the two adjustments that affect only sideband.
73
I think I have gotten it working better how the smaller signals read a bit lower but the bigger signals are normal. Example on my other radios and I am getting a 7 on the radio I shows 7 how ever if some one is ,3 on the other radio it shows make between between1 and 2
Yep. That radio has lost only part of its sensitivity. One of the most frustrating faults to troubleshoot is a radio that's doing 8/10 or more of what it should. Not enough to perform properly, but not dead either.
Call it a subtle problem. This is why looking for a "subtle" clue is important.
If EVERY, SINGLE LAST small tuning slug is peaking with the top of the slug visibly below the rim of the hole, that will cross a defective IF/RF transformer off the list.
Only takes one of them with that "flush to the rim of the hole" fault to hold the radio back this way.
73
Call it a subtle problem. This is why looking for a "subtle" clue is important.
If EVERY, SINGLE LAST small tuning slug is peaking with the top of the slug visibly below the rim of the hole, that will cross a defective IF/RF transformer off the list.
Only takes one of them with that "flush to the rim of the hole" fault to hold the radio back this way.
73