🚀 go-pugleaf

In article <1cnkl8INN4gj@bigboote.WPI.EDU> bhiller@bigwpi.WPI.EDU (Brent Hiller) writes:
>I recently build a Ramsey 2 meter ham radio transceiver. The radio
>seems to work pretty slick, but there is one problem. I recently installed
>it in my car. Works great when the car is not running, but when you
>run the car the radio picks up a very large amount of alternator or
>ignition hum. I was able to reduce it by running a dedicated power
>line back to the battery and the ground connects to a screw in the
>engine compartment. I also put a $13 radio shack filter just before the radio.
>All of this helped to reduce the hum but I still can't get rid of it. I
>tried hooking the ground directly to the battery but the hum got worse.
>I am looking for any suggestions that can help get rid of this hum. Any
>circuit diagrams for filters used in commercial radios would
>also be appreciated.   Also, I'm looking for any mods to this radio that
>would help improve its receive sensitivity.

Check the engine ground strap connections for corrosion. The tipoff is
the noise getting worse when you bring the radio ground to the battery.
It should have gotten better. You're getting ground return currents
through the radio, via the antenna ground and back to the battery, 
because the normal path, the engine ground strap, has developed high
resistance. That's a theory anyway.

To get more receive sensitivity, stretch the coil connecting to the
UHF connector to almost twice it's as shipped length. I posted a whole
bunch of mods to the amateur radio newsgroup a few months back, including
a way to keep the transmitter from transmitting while the VCO is sweeping
into lock. If you don't do this, you'll annoy every repeater owner on
2 meters.

Gary KE4ZV