Not quite amatuer radio.. mwbb aka am radio

[VE7NOT]

I understand this today. The 3m band (fm bb) makes most am/fm antennnas on cars quite good on fm.

Now for am it is of course a compermise.

However I note the sensitivity on am radios in cars is HUGE. I pick up sacremento stations in the evening on the small stock whip like they are fm almost.

But it makes me think... the old days before 3m fm.

am broadcast was all thre was. A simple 12v receiver and small whip? http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif

This makes little sense to me.... the 1950's- >>>>>>.

http://www.qrz.com/iB_html/non-cgi/emoticons/rock.gif why use small whips? In those days it would be simple to use a continuous coiled antenna. Would have been better for am mobile. Hey my 75m hamstick was doing great on am rxing http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif when it was in the car and I used my ham transceiver for am rxing then.


I have seen pictures of antenna tower form the 1920s with antennas..... as a line running at a 45 degree angle away from the top of the tower. Simple txing.. but I mean did they really use simple whips for am rxing then?

[VE7NOT]

Bump.. Time for new stock antennas on vehicles. http://www.qrz.com/iB_html/non-cgi/emoticons/tounge.gif

[k8jd]

The tube AM car radios I grew up with had a lot of rf gain in them and used high Z input circuits and a siries capacitor called a trimmer that u tuned at 1400 kHz to match the antenna whip. look at the cross section of the coax in a car radio antenna feed. It has a verrry thin center wire and is aboout 400 ohms or some high value Z. My first BCB DXing was done with a car radio. often heard KOA in Denver and KSL in Salt Lk City and a few times KFI in LA, while sitting in my driveway in suburbs of Detroit!

[AG3Y]

You couldn't beat the old AM Car radios for DXing on the Broadcast Band! They were so good, that some people still have some of the earlier transistorized models, hooked up to a 12 volt power supply for AM dxing!

I have an old Caddy radio that still will outperform anything else in the house! It's an ugly brute sitting there all by itself, but wow! what performance!

73, Jim

[WA7KKP]

The old AM car radios had a high impedance antenna input that is similar in operation as the active antennas you see today.

Look at an antenna lead -- it is coax, but has a very fine wire down the middle tube, that is to minimize capacity to ground. The trimmer cap in radios was tweaked to help compensate for that.

And car radios commonly had a 262 kHz IF, a bit tighter than the 455 IF's of today, and usually had a tuned RF stage, where most BCB radios didn't. They were designed to work in a more hostile environment, and better, so you didn't have to dismantle the dash every week to keep it working. The exception to the rule were the hybrids, that used 12v DC for the plate voltage as well -- most of these were underwhelming in sensitivity.

Since FM took over the airways, good AM has gone the way of hetrodynes all over the band when the night-time power reductions were eliminated. Only a few clear channel AM's still rule and I don't care for their programming anymore.

Maybe that's why Sirius and XM Radio exist . . . .

Gary WA7KKP