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Vexed !!

Posted: Sun Jun 17, 2018 11:53 am
by illllm
So i got this pocket HD radio a few days ago and I was experimenting with it. My plan was to improve its antenna. I have a miniwhip in the attic and a few other antennas that I used with RTLSDR. I tried all of them and using them this HD radio would barely pull in normal FM signals. So out of curiosity, I plugged in the regular ipod/walkman style headphones and lo and behold i was receiving about 8 HD stations and sub-channels. So I started experimenting with different options. I plugged in a head phone sharing adapter, plugged in the headphones in one slot and the cable to my amp to the other. no signal. I remove the cable to amp and it picks up some stations.

Any ideas what is happening ?

My theory -

1. Headphone shield cable is antenna. Connecting to car aux or amp aux is grounding the signal.
2. Tuned circuit for antenna and will not tolerate long cables to amp?

How do I separate this? I would like to be able to plug it into an amp and into the car.

Re: Vexed !!

Posted: Mon Jun 18, 2018 12:59 am
by rtlsdrblog
Yeah a lot of portable radios and phones use the headphone cable shield as the antenna.

Try connecting the shield to the antenna output instead.

Re: Vexed !!

Posted: Fri Jun 22, 2018 9:45 pm
by illllm
Would it be possible to add some filter

Headphone jack -----Filter to allow only audio frequencies ----- plug into amp
-----Single wire antenna to ground in head phone jack