[Milsurplus] TBX info...correction in red

[w8au at sssnet.com]

At 10:25 AM 2/14/2017, Ray Fantini wrote:
>Do recall accounts of later at Tarawa where radios like the TBX were 
>considered completely unsuitable requiring a large crew and being 
>low powered and when possible a jeep mounted TCS set was far 
>superior. The Navy and Marine units did not appear to have a lot of 
>good choices for short range communications early in the war with 
>sets like the TBY and TBX...et al....

Ray:  The TBX was for short range work, as you said, but it was 
patterned after the work of the U.S. Forest Service SPF portable 
radios designed about 1930
for use by smoke jumpers. Their Montana radio group, consisting of 
about 8 hams, designed and built these before small portables were 
available.  Portable radios  did not appear commercially until after WW2.

The SPF put out 2 watts at frequencies just below 3.5 Mhz and used 
low antennas.  This allowed them to use ionospheric layers for 
reflection purposes, getting signals straight up over the trees and 
coming back down between the trees...instead of trying to get ground 
wave signals through all the foliage. USFS was interested in only 
covering up to 20-30 miles.  They actually developed what we call 
today as NVIS propagation. which was also used by our military in VietNam.

The Navy adapted the SPF design but reviewers opined that the TBX was 
not as effective. However, it was much more rugged, which was 
critical for military use.

Interestingly, amateur radio involvement in USFS, and its results, is 
part of our heritage, although not well known.

Just some trivia for you all....;-) (not sure if the SPF pic will 
make it though the milsurplus reflector)

Perry   w8au



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20170215/194d4476/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SPF action.jpg
Type: application/octet-stream
Size: 68434 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20170215/194d4476/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SPF USFS.jpg
Type: application/octet-stream
Size: 66229 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20170215/194d4476/attachment-0001.obj>