[Lowfer] Aircraft Automatic Direction Finders for Beacon Monitoring

[Mike.WE0H]

I have a yellow tagged KR-85 which does receive the 600m band well but 
is very broad. I've used it a few nights, always hears the stations but 
all of them at once...hi hi...1kc tuning steps. The AGC handles 
summertime lightning static very well.

Bought it cheep enough a few years ago. Wished I had the loop antenna 
for it and an indicator. The sense antenna is nothing to homebrew.

Mike
WE0H


Tom Clifton wrote:
> I have several dead King KR-85 ADF untis that I want to  repair and press into service as 505khz beacon monitors.  Designed primarily for receiving 200khz to 500khz non directional beacons, they came out of 1970's vintage private planes and to date I have not been able to come up with a service manual with schematics (short of paying $70 for a manual  at Esso Air). Is there any chance that anybody out there may be able to assist with at least a partial copy of a manual
> 
> These things are interesting - run on 12 volts, typicaly have an IF strip in the 150kc range and have a "digitally generated" vfo that has a TTL divider chain and a PLL for generating a sine wave.  BFO included!  And the front end  on these things have pretty good input filters divided into three bands - 200khz-400khz, 400khz-800khz and 800khz-1600khz (Yup - covers the AM radio band) to reduce intermod fro out of band stuff.  Conversion to 137 or 185khz would be awkward, but theoreticaly should be possible, likewise conversion to ham 160m...  They have a balanced loop input as well as an unbalanced sense antenna - lots of ham potential!
> 
> 73 - Tom in St. Louis