HOW TO CONVERT AM
BROADCAST RADIOS TO RECEIVE ONE SIXTY METERS.
If you don't have
a general coverage receiver you can convert an ordinary am wireless. As
broadcast sets cover up to about 1630khz it is possible in most cases to tweak them upto above 1.8mhz.
With a signal generator
and other service equipment the job is easy but I will explain how to do
minimal gear.You will need two radios, one to be converted and the other to use as a signal source. Try to
pick a nice sensitive one for the conversion to one sixty, as am radios can be picked up for a few dollars
at junk sales these days it should not be to hard to find a suitable one in fact its often possible to obtain at
very reasonable cost a general coverage set that covers the band, but most miss out on the lower Short
wave portion of the spectrum. I have not had much luck converting a set from 2.3mhz down to 1.8mhz.
Back to the instructions,
first tune the signal source set to about 1400khz this will, assuming a
stage as in 99% of sets put the local oscillator on about 1855khz which can be used as a local signal in the
set to be converted identify the local oscillator coil and slug, its usually painted red and when turned
it changes the stations, what you want to do is adjust this so all the am stations move down the dial. Put
the two radios near each other and tune the to be converted set to the top of its dial ie the hf end, adjust
the coil until you come across the carrier from the local osc of the set being used as a signal source. In
most cases this can be achieved without to much trouble. The next step is to tune up all the rf and ant
stages so they peak on one sixty this can be done by listening to the band noise and and adjusting for
maximum sensitivity, for a wide band noise source go near a light dimmer or flouro light and tune for the
Some times one can not obtain much sensitivity this is usually due to the fact that even with all the
trimmers fully out the stages will not resonate high enough in frequency, this is bit of a problem but often
one can just disconnect the trimmers and it will peak ok on one sixty, the problem with this is that the
tuning won’t track so it will be very deaf on the normal broadcast band but since most people have plenty
of radios to listen to it doesn’t matter, you can fiddle with r/c values and the rest but it all takes time so if
a set is hard to convert just try another one.
Car radios are very
good but hard to change, the simplest method is to remove all the ferrite
the inductive tuning arrangement, this will make it resonate close to 1.8mhz and use the local osc coil
slug to tune in the stations.
Although we use AM
because of the volume and clarity and easy reception with cheap radios,
a lot of the
stations heard will be on ssb, to hear this just use the local oscillator of another radio as a bfo, this system
works quite well on these frequencies, depending on the strength of the signals heard change the
distance between the two sets for the best result.
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