Johnson Messenger 4730 CB radio - Page 1
Forum section: electronics / rf-microwave

author: WB8PFZ
author_rank: Regular Contributor
timestamp: April 02, 2021, 07:50:18 pm
content: I purchased one of these that has been modified to work on the 10 meter band. My question is will this receive without the microphone? I know some radios will. I do not have the mike and it does not receive. Thanks Mike

author: bob91343
author_rank: Super Contributor
timestamp: April 02, 2021, 07:58:36 pm
content: Get the manual. That should answer most of your questions.How do you know it doesn't receive? The 10m band is very sporadic and when I listen I usually hear nothing.

author: WB8PFZ
author_rank: Regular Contributor
timestamp: April 02, 2021, 09:53:14 pm
content: There is no audio.

author: WB8PFZ
author_rank: Regular Contributor
timestamp: April 02, 2021, 09:54:16 pm
content: Instead of buying a manual I would buy a microphone if that would solve my problem.

author: bob91343
author_rank: Super Contributor
timestamp: April 03, 2021, 02:30:04 am
content: Sometimes, but rarely, there is a jumper in the microphone cord that interrupts the audio. However, that being unlikely, you need to find the problem. Bad speaker, open circuit, etc.Open the radio and start troubleshooting.

author: xrunner
author_rank: Super Contributor
timestamp: April 03, 2021, 02:36:28 am
content: Quote from: WB8PFZ on April 02, 2021, 07:50:18 pmNot enough information ...You say it "does not receive", but just because there is no audio does not mean it isn't receiving. Does it have an s-meter? Does it indicate a noise level or a signal level? If so there might be a problem with the speaker. Do you have a scope? If so see if there is an audio signal output to the speaker. So much more to check too ...

author: WB8PFZ
author_rank: Regular Contributor
timestamp: April 03, 2021, 03:06:29 pm
content: Yes, I have lots of test equipment. A former worker that was in the Airforce as a tech once told me if he was caught working on a piece without having the manual opened to the correct page the shit would hit the fan. I can buy a Sams manual but I hoped I could get a simple answer here?

author: A.Z.
author_rank: Super Contributor
timestamp: April 04, 2021, 09:58:39 am
content: according to the mic plug pinout found here (near bottom of page)http://www.in3eci.it/index.php?fl=4&op=mcs&id_cont=391&eng=from%20ASTATIC%20to%20WATSON&idm=435&moi=435the 4730 does not exclude the speaker if the mic is unconnected, so I believe your best choice would be finding a schematic and then trying to find why there's no AF output

author: xrunner
author_rank: Super Contributor
timestamp: April 04, 2021, 11:05:05 am
content: Quote from: WB8PFZ on April 03, 2021, 03:06:29 pmI asked you several very simple questions , and you couldn't (or wouldn't ) answer them.I am left wondering why.

author: Stray Electron
author_rank: Super Contributor
timestamp: April 04, 2021, 06:11:42 pm
content: Quote from: WB8PFZ on April 03, 2021, 03:06:29 pmMore than just SHTF, you could be, or LIKELY would be, subjected to non-judicial punishment, aka an Article 15. I think that the same is true in all branches of the US military and probably true in most modern militarys. Most technicians at that level are neophytes and the military doesn't want to take chances with their very expensive equipment. That's also why they go to a lot of trouble and expense to provide service manuals, etc.

author: CJay
author_rank: Super Contributor
timestamp: April 08, 2021, 09:15:02 am
content: Quote from: WB8PFZ on April 02, 2021, 07:50:18 pmThe answer is 'Depends', most CB radios that use a relay to switch between TX/RX don't need the mic, many transistor switched radios do but it's not an absolute, I have some relay ones which need a mic to 'enable' the speaker and some transistor switched ones which don't.There are numerous CB mic wiring guides on the 'net and I don't think it would be at all difficult to find the relevant pinout for your radio, if it does have an RX line on the Mic socket then I would try jumpering that to ground.It's also worth testing with an external speaker, I've found several old radios with broken, faulty or badly tarnished ext spkr sockets that cut off the internal speaker.Hope that helps.

author: cdev
author_rank: Super Contributor
timestamp: April 08, 2021, 06:53:45 pm
content: is it clean? I'd expect it to be perhaps as good as it gets with CB gear, coming as it does from EF Johnson.Is it AM only?No, its a 40 channel SSB/AM radio..What frequencies did it get converted to use?Thats my biggest question..How does it sound on the air?