[Milsurplus] LO radiation and the TBX

[Mike Morrow]

Ray wrote:

> My point in all of this is that when the TBX was redesigned
> to the eight series their was a number of improvements to
> the radio, remote capability, improved audio, CW side tone
> and a separate MO for the transmitter, but they still had no
> stage of RF amplification for the receiver.

I've heard or read speculation over the years that the TBX-8 never made it to service before WWII ended.  It's always seemed to me that all the work that went into re-making the TBX-8 was pretty pointless in such an obsolete sow's ear system.

>Just a mixer coupled to the antenna. If the Navy had any
>concerns about LO radiation why did they not address it then?

I don't think any convincing evidence exists that there was any concern, nor need to be concerned, with LO radiation, especially for sets utilized as the TBX was.

>the TBX was eventually replaced by better radios long before the wars
>end, and by comparison in the Army they had two stages of RF in the
>BC-342, BC-312 and BC-348 receivers, maybe for twice the isolation?

The USN's MAB/DAV HF portables lacked RF stages, while the Signal Corps' BC-611, BC-654, and BC-1306 sets have one RF stage.   I believe that the USN's other HF "portable," the RBM, has two RF stages, and the RBZ has one, as does the TCS, RAX, ARA, and ARB.   However, the real point of having one or more tuned RF stages in a low IF, single conversion receiver covering a large frequency segment (i.e., BC-312, -348) is to improve image rejection, not to reduce LO radiation.   The TBX frequency range is pretty narrow, and image response was likely not a worrisome problem in its intended operating environment.

73,
Mike / KK5F