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Reviews Categories | Transmitters: Commercial/Military/Marine adaptable to ham use | TBX-8 MILITARY Help


Reviews Summary for TBX-8 MILITARY
Reviews: 1 Average rating: 4.0/5 MSRP: $Unknown
Description: TBX-8 Military Transceiver manufactured by Garod Radio Corporation April 1945.
Product is not in production.
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JAMES_BENEDICT_EX_N8FVJ Rating: 4/5 Dec 6, 2001 22:40 Send this review to a friend
Stabile Receiver  Time owned: 0 to 3 months
The TBX-8 is a NAVY WWII transceiver that receives from 2.0khz to 8.1khz and transmits 2.0 to 6.0khz. Actually performs perhaps 160 hz beyond band design and is simple to extend to cover the full 160 meter band. The power output is 30 watts CW and 3 watts beam plate modulated AM. Beam plate modulation is the prefered design regarding low level modulation that has good quality audio. The receiver is a superhet design using five tubes for single conversion and not having an RF amp. The use of the signal directly to the converter tube is usually a benefit for such simple designs. Two issues makes this a very usable receiver is the build quality is 'out of this world' and I used a fully regulated power supply. These two items adds to a stability that is just fine for listening to SSB. Fortunately the BFO is rock solid and produces a clean signal of wide frequency adjustment. The 1.5 volt DC filament tubes produce very little temperature rise which adds to the stability (LM-350T regulator produces -80db output). I replaced the 1N5GT with a 1P5GT in the BFO section and replaced the 1A5GT with a 1Q5GT for the audio output. The stock audio is about 100mw and the beam tube 1Q5GT produces 350mw. I also changed the audio transformer from 20k to 2500 ohm to 8k to 8 ohm (see AES in Tempe, AZ). The 350mw audio is quite loud into a Radio Shack #21-549B remote speaker. In fact, this speaker compliments the radio as the audio is better than my SB-600. This is not true on my other HF radio. I also installed a .0005 ceramic capacitor at the 1Q5GT grid to ground to remove some high frequency responce which is not needed or wanted. The transmitter uses a rugged 2E22 with a directly heated filament. I suspect a 6CA7/EL34 could replace this tube if stock dries up in the future. Loading and tuning is simple using the RF current meter. The transmitter has two crystal control positions or a VFO. The receiver is VFO only. The radio has a 'spot' frequency control for tuning the transmitter to the receiver. The radio has a built-in antenna relay and operates full break-in. As for the power supply I converted a Drake AC-4 to provide 500v, 90v, -4.5v, 1.5v, 12v and another 12v RF isolated from the first 12v. All except the 12vdc is regulated. If you want AC-4 conversion details, please email me for a schematic. As for AM power I use a converted tube type CB linear amp. The 3 watts carrier is perfect for this application and a simple bandswitch and new tank coil completes the conversion. I would not suggest solid state as without a tank circuit in the output you may find TVI and other issues present. I find this radio to be very friendly to operate and more of a 'normal' looking transceiver not so far removed from amateur equipment of the same era. For better selectivity, a DSP filter in the CW mode is a perfect addition. The receiver does not require an aftermarket RF preamp as the sensitivity is unusally high for the design. My radio is serial number 383 which suggests less than 400 where manufactured. I was told this radio was one of a few used by the famous WWII 'code talkers'. The code talkers were never successfully decoded during WWII. Their action saved many lives.
 


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