The RA137A/RA37A are longwave convertors for the RA17 series of receivers.
They cover the frequency range of 10-980 khz.If you have ever wondered why there is a red scale below the black main tuning on the RA17 film scale now you know,it is for tuning when using an LF adaptor! It is not a logging scale as I have heard some people comment.
Both units were produced in two versions ,one for the Europeans the other for America.The only difference between the two units is that the RA137 has a tuning scale for the pre-selector.
The controls from left to right are as follows.Attenuator0-40db,Aerial range(pre-selector),Pre-selector tuning,Power ON-OFF,HF-LF selection for the main receiver.
Adding one of these convertors to an RA17 can make a useful addition to an excellent receiver.
Connection is made to the RA17 by means of the RF and 1 mhz osc outputs on the rear of the receiver.The HT line has to be broken on the terminal block at the back of the receiver and connected to the convertor to enable switching between HF/LF
There is also an RA237 model which was made specifically for the RA117.It has an extra filter fitted as the RA117 does not have a tunable 2-3mhz filter.
There are four versions of the RA137. The RA137A as described above. The RA137B is the north American Version, the RA137C is a modified version for use with the RA78E and the RA137D modified for use with the RA78F.
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