'67 AM-FM radio Judging question...

[Patrick T.]

my radio seems to work OK; it's easy to find a station on the FM side. AM radio stations are much harder to find on the dial, although it depends pretty much where the car is located. I get static all through the AM band and occasionally will get a station you can listen to.

My question is...if I'm getting my car judged at some remote Chevy dealer and during the OPS check all I can get is static, will I get a point deduct? A master judge I talked to said if all you can get is static at that particular location, it still shows the AM is working and therefore, no deduct. What do you think about this or is it written somewhere? Thanks, PT

[Chuck G.]

Re: '67 AM-FM radio Judging question...

I ran into this situation when I had my 54, PT. Can't remember.....might have been Hershey, PA, or maybe Seven Springs, PA.

Could barely catch 1 or 2 AM stations. Of course, with the very few or non existant AM stations, the Wonderbar wouldn't stop on multiple stations, as there was no signal.

I wasn't the only one with this problem. I don't think I got a deduct.

Chuck

[Tom H.]

Re: '67 AM-FM radio Judging question...

This is just me and I am a full blown rookie judge at the chapter level, but I would probably make no deduction. I would however note that no stations were received on the AM side during judging.

[Bill I.]

Re: '67 AM-FM radio Judging question...

Pat. There is a trimmer pot behind the treble control. Set radio on Am around 700 and adjust for max static. This may help. Bill.

[Jack H.]

Re: '67 AM-FM radio Judging question...

I disagree with the judging advice you've been given. Why? Been there done that...

The 6V cars are well known for having troubles with weak AM reception. But, later Corvettes are NOT.

When we held the National Convention in Sun Valley, early, 6V, C1 cars were failing the radio portion of the Operations Check. Plus, the first handful of PV's that were conducted were questionable as the few C2 cars that ran the course were only picking up ONE AM station.

Several NTL's approached me as my '71 (there for Founder's Award) has a modern AM/FM/Cassette/CD in it. I could capture the one AM station that was broadcasting locally, and get 'fuzzy' reception on distant AM stations.

The test policy for that site changed to being (1) waive AM reception for 6V C1 cars and (2) accept later cars that could lock/capture the Sun Valley local AM station...

The reason for checking both AM and FM reception is that it's a well known fact that AM reception is VERY sensitive to the quality/integrity of the antenna and lead-in cable. FM reception is much more forgiving and only tends to show problems under 'fringe' FM reception conditions.

A common restoration issue is the care & handling of the radio lead-in cable from the antenna when the car's interior is being 'gutted' and fresh/new carpet is being installed. The actual conductor inside the cable is VERY thin (controlled capacitance profile) and prone to fatigue fracture if the cable is mishandled (severe bending/twisting).

So, it's not uncommon for restored cars to exhibit poor AM reception vs. 'decent' FM reception as a result of damaged antenna lead-in cables...

As mentioned in several previous posts (see archives), the easy 'acid test' is to gently unplug the car's existing antenna cable from the rear of the radio chassis (banana plug) and temporarily install a substitute cable & antenna.

El cheapo antenna/cable combos can be purchased at WalMart for $10 or less. Plug in the substitute and have a helper walk it through the open door towards the back of the car getting it as far as possible away from the engine compartment.

If the radio IMMEDIATELY demostrates improved AM reception, you've got a problem with your antenna cable and it's time to buy and install a replacement...

Last, remember, at a given meet (Chapter, Regional, National) there will be cars on the judging field similar to yours. The judges will KNOW what to expect and what the performance yardstick is for that meet/that location!

[Terry M.]

Re: '67 AM-FM radio Judging question...

You might hope your's is not the only Corvette being judged. I have been at meets where even "modern" cars didn't get radio reception on one band and/or the other; and all the Corvettes were given a pass. On the other hand if one Corvette of your generation gets a station -- then they all should. The judges usually compare notes to see what the local conditions are, and the folks who live in the area usually have a good handle on what the radio performance is expected to be.

[Jack H.]

Re: '67 AM-FM radio Judging question...

The trimmer pot is NOT! It's a variable capacitor you're turning to center the capacitive load of that specific antenna and its mating lead-in cable to your radio chassis. Antennae are capacitively coupled...

Tweaking the trimmer will only yield 'modest' performance improvement under severe fringe reception conditions. In a major metro area, with robust AM signal strength, adjusting the trimmer results in little/no observable difference.

So, if your modern passenger car gets decent AM signal reception, that's the yardstick for your 12V Corvette radio in AM mode...

[Tom H.]

Re: '67 AM-FM radio Judging question...

I disagree with the judging advice you've been given. Why? Been there done that...

The 6V cars are well known for having troubles with weak AM reception. But, later Corvettes are NOT.

When we held the National Convention in Sun Valley, early, 6V, C1 cars were failing the radio portion of the Operations Check. Plus, the first handful of PV's that were conducted were questionable as the few C2 cars that ran the course were only picking up ONE AM station.

Several NTL's approached me as my '71 (there for Founder's Award) has a modern AM/FM/Cassette/CD in it. I could capture the one AM station that was broadcasting locally, and get 'fuzzy' reception on distant AM stations.

The test policy for that site changed to being (1) waive AM reception for 6V C1 cars and (2) accept later cars that could lock/capture the Sun Valley local AM station...

The reason for checking both AM and FM reception is that it's a well known fact that AM reception is VERY sensitive to the quality/integrity of the antenna and lead-in cable. FM reception is much more forgiving and only tends to show problems under 'fringe' FM reception conditions.

A common restoration issue is the care & handling of the radio lead-in cable from the antenna when the car's interior is being 'gutted' and fresh/new carpet is being installed. The actual conductor inside the cable is VERY thin (controlled capacitance profile) and prone to fatigue fracture if the cable is mishandled (severe bending/twisting).

So, it's not uncommon for restored cars to exhibit poor AM reception vs. 'decent' FM reception as a result of damaged antenna lead-in cables...

As mentioned in several previous posts (see archives), the easy 'acid test' is to gently unplug the car's existing antenna cable from the rear of the radio chassis (banana plug) and temporarily install a substitute cable & antenna.

El cheapo antenna/cable combos can be purchased at WalMart for $10 or less. Plug in the substitute and have a helper walk it through the open door towards the back of the car getting it as far as possible away from the engine compartment.

If the radio IMMEDIATELY demostrates improved AM reception, you've got a problem with your antenna cable and it's time to buy and install a replacement...

Last, remember, at a given meet (Chapter, Regional, National) there will be cars on the judging field similar to yours. The judges will KNOW what to expect and what the performance yardstick is for that meet/that location!

I would say that is the best answer to a new question as I have seen in a long time. I will judge accordingly in the future. Good answer. Thanks.

[Jerry R.]

Re: '67 AM-FM radio Judging question...

Just wanted to mention that adjusting the antenna trimmer (recessed screw head located behind the tuning knobs which are removed for access) should not be adjusted to 700 on the AM dial as mentioned above. The correct setting is 1600. Try to find a weak station near 1600 and turn the screw back and forth slowly for maximum loudness. Doing it at 700 KHz will severely detune the circuit weakening reception. This only applies to 63-67's and only on the AM band.

Also, if it doesn't peak the signal, this 'may' indicate a feedline problem as mentioned above.

Jerry

(info is from the 67 Delco radio manual alignment section)

[Bill I.]

Re: '67 AM-FM radio Judging question...

Jerry, you are correct. Don't know where I came up with 700kc. Could it be 67 years? Naw,can't happen. Now where were we? Bill

[Jerry R.]

Re: '67 AM-FM radio Judging question...

No biggie for sure Bill. Re-wording the old joke seems to fit -> How many forum members does it take to correctly restore a given year Corvette? LOL

Guess I've seen too many radios over the years BUT, I do remember seeing one (a vette I'm pretty sure) that did adjust to that setting. If the mixer used a reverse side injection at the oscillator/mixer circuit, it might just make sense. I'll check the 53-57 adjustments tomorrow.

All this trivia in my head and I still can't adjust a carburetor - but the radio works.

Thanks! _Jerry_

[Jim C.]

Re: '67 AM-FM radio Judging question...

Patrick,

I had my 1966 judged in 2007. I think a pretty top notch guy judged my interior and operations, including the AM/FM radio. He was VERY fair, but consistently deducted points when he found things that were not right. I think he did a good job and really took his role seriously. I did loose some points on operations issues. So, I know he would have deducted points for my radio if he thought something was wrong. I got just ok FM reception and mostly all static on the AM side. He did not take a deduction, saying the radio worked but the reception was poor due to the event's location. I'm not a judge, but that was my experience. Static might be ok.

Jim C.