AM Car radio with long wire antenna for BC band DX - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: October 14, 2025, 01:59:01 am
content: Car radios generally have pretty reasonable performance and can often be had for zero cost. I'm interested in playing with one for broadcast band DX. What would be the optimum way to connect a long wire antenna into such a radio?The usual feeder coax on a car radio antenna has a certain amount of capacitance, and often there is a trimmer adjustment on the radio to match to this somehow for best results. Does this adjustment matter if I simply connected 10 metres or so of wire?

author: xavier60
author_rank: Super Contributor
timestamp: October 14, 2025, 02:20:06 am
content: Quote from: Circlotron on October 14, 2025, 01:59:01 amAssuming it is the old permeability tuned type, and you want to be able to peak the antenna trimmer, a series compensating capacitor needs to be put in series at the antenna input socket. Start with 100pF. And if possibly won't make much difference to reception anyway.From my experience, a long wire antenna tends to add more interference without actually receiving many more stations.Hopefully, your experience will be better.

author: Circlotron
author_rank: Super Contributor
timestamp: October 14, 2025, 03:21:04 am
content: The radio is out of a late 90s Toyota Camry and the tuning is entirely electronic. And it doesn't appear to have an antenna trimmer for some reason. I thought all car radios did. Definitely much older ones had them.Would it still need a series compensating capacitor?

author: xavier60
author_rank: Super Contributor
timestamp: October 14, 2025, 04:50:49 am
content: Quote from: Circlotron on October 14, 2025, 03:21:04 amI can't be certain, it might still have band pass filtering in the front end and expects to see a certain amount of antenna capacitance.Possible problem could be overload from a local station.

author: CaptDon
author_rank: Super Contributor
timestamp: October 15, 2025, 12:06:41 am
content: If you want a really hot BCB car radio receiver then look around for something solid state from the mid 60's to around '71. And you want a 262KHz I.F. not the newer 455KHz. I had a 64 Pontiac BCB AM only and it was BY FAR the most sensitive AM radio I ever owned!! I used it with one of those old Gonset SW to BCB converters and it was incredible how nice AM shortwave broadcasts sounded coming from that car radio. The Gonset had 2 or three tubes in it and needed a filament supply and +150VDC for the plates. Since it was used at home on the bench I built a very simple 120VAC power supply which powered the Pontiac radio as well as the Gonset converter. Cheers mate!!

author: xavier60
author_rank: Super Contributor
timestamp: October 15, 2025, 01:15:18 am
content: The best AM car radio I know is the Clarion RU140A/B. Expect to pay ~$100 on ebay. I use them in the tractors on a remote farm where FM reception is too weak to receive, leaving only AM.My main interest in AM is in widening the IF bandwidth for better sound quality, mainly on non-DSP portable radios.Our local AM station can sound quite good on a wideband receiver.

author: jonovid
author_rank: Super Contributor
timestamp: October 18, 2025 05:52:23 am
content: try a tuned circuit loop wire antenna on a pedestal this will give your noise null out rejection for broadcast band DXwith a 2 turn feed loop going to your AM car radio.