[Milsurplus] LO radiation and the TBX

[Bob Wilder]

At 01:10 PM 3/28/2005 -0600, Mike Morrow wrote:

>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

Think Mike hit the answer.  The IF of the TBX is 1515 KC with 2-8 MC RX and 
2-5.8 MC TX.
This was the radio of choice of the code  talkers with 3W AM and 9W CW.



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Bob & Carole Wilder
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