Re: Tracing receive signal for low signal
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Possible, but unlikely ...As a first step tie the wire loop you wound thru the core to the input of your scope..measure the signal from tp2 to the scope across the bandwth you can sweep with your generator..look for any peaking/dropouts across the bandwidth .. when I didn't have the SA/TG I now have, I made 2 identical RF probes ...Hooked one to one channel of scope, and one to the other ...Used one to monitor the input of a circuit and the other to monitor the output ...Sweep manually the frequency and looked for peaking/dropping/changes and wh y those occurred ... I also constructed 2 identical RF attenuator boxes ..3db,6db,10db,20db,20db. with bnc connectors on each end (still use them) to set levels and verify overload/distortion issues .. Took HOURS to sweep/characterize circuit ..
Now it takes longer to hook up ths SA/TG than it takes to measure a circuit ..but its still doing the same thing Its best to start at the "back end" of the circuit and work towards the front ..fixing one problem at a time Virtually all the "gain" in this receiver is in the audio stages ...
Stage by stage ...Input low-pass ....Probably -3db loss
??????????????????????????? T1/T2 Mixer? .....Minimum 6db loss (probably more) ??????????????????????????? Q10/12 amp??????? 15 Db gain Maybe .. ??????????????????????????? 45 Mhz BPF?????? minimum 6 db loss (probably more) ??????????????????????????? T3/T4 Mixer ....Minimum 6db loss (probably more) ??????????????????????????? Q30/32 amp?????? 15 Db gain Maybe ??????????????????????????? 12 Mhz BPF??? minimum 3db loss (Probably more) ??????????????????????????? T7 mixer .....Minimum 6db loss (probably more) Add all those up ....Losses Minimum 30 Db ///Gains ...Maximum 30 Db .... To get from 1 uV (microvolt) to 1 V (volt) you need 120 Db gain .. All that has to happen somewhere between Q70 and whatever you are using for a speaker Fix the audio?? then (probably) most of these other issues will solve themselves
Jim
On Tuesday, December 25, 2018, 12:39:31 PM PST, Dave Space <davesspacebar@...> wrote:
Gave it a try same results 1900uv estimated at tp2 to get to .1p-p
9000uv estimated at tp1 to get .1p-p? (I think I reported my signal generator's input in my message last time and mentioned uv when it was really mv 900mv through a -40b attenuator so estimated at 9000 uv.)
with the wire wrapped through about 5 times (it was about as many as I could fit and it's even thinner magnet wire than they used on T2 itself.)
So perhaps that means its not matching that is the issue?
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