Useful information ...maybe!

This is basically some information that i thought was useful when bulding various projects or fixing things i have broken..!!


Project info


SHW5177 800-1000MHz 5W amplifier as seen on ebay

Below is the gain plot of the module

As you can see it's not much use at 23cm but i will open it up and see what's inside!



Inside the module...


It is extremely difficult to remove the cover..!

The cover is soldered to both the rear plate/heat sink and the cover, i used a hotplate at 200c to lift the cover and board off in one go, the gold under the FET's was soldered to the back plate too so be very careful if you try it!

I have had a couple of attempts at re-tuning it for 23cm but No luck so far... I have only managed about 8dB gain max at 1280MHz even by removing all tuned areas.. so no use yet really!




4MS DATV @100W peak with my current home-brew setup

Shoulders of filter @-27dBc

IMD3 & 5 visible but could be worse!






23cm Comtech moduel IF Notch

If like me you have terrestrial breakthrough in your 23 or 13cm ATV receiver then you will need a notch filter on the Antenna input to fix the problem..

With a receiver that uses a 70MHz IF then this will not likely a problem but most use 480MHz IF filters..


My Local signals are:

474MHz Digital from Bilsdale

482MHz Analogue from Pontop Pike

490MHz Analogue from Bilsdale - The main culprit!


A simple way to fix it is to use a coax stub notch on the antenna input of the receiver but if you have multiple signals spread apart a wider notch is desired so i make this up using Elsie simulator..



I fitted the filter inside the back of the tuner can where the input connector is soldered using surface mount components but you could make something external with the same effect i'm sure.





It will look something like this but mine appeared about 20% wider due to component tolerences..













FT-857 - VHF TX/RX Fault, low power o/p, poor receive.

Loose earth tag/spring underneath the board caused s/c where the duplexer is for V/UHF, Resoldered.


FT-736R - PSU Tripping constantly at power up

C9 in PSU leaky and probably the same for most of the others in the same area due to heat, replace with 105C rated ones.









Updated May 2011