This looks like an aircraft communications transciever for the UHF aircraft band (225 to 400 MHz), probably designed in the mid 1970's. The power supply looks to be a linear voltage regulation drawn from a 3 phase power transformer. Switching power supplies were non-preferred due to the EMI they generate and high power bipolar switching transistors are relatively slow compared to FETs. The only problem is, I don't see any large bulk filter capacitors. You don't need that much filtering though with a 3 phase, full wave rectifier with a 115 volt, 400 Hz line. The RF power amp (or transmitter) is linear and low level modulated using bipolar transistors. Those hybrid splitter/combiners may be the 90 degree type, which are used to isolate the parallel outputs for reduced distortion. My best guess on the output power is 100 watts CW, with 95% AM modulation capability. DC power needed for the RF power amp is probably 28 Vdc at 20 amps. The receiver probably uses 3 pre-selectors to cover the broad frequency range. Using 3 pre-selectors also reduces the signal level across the varactor diodes, which reduces intermodulation distortion. On an aeroplane with multiple communication transceivers, due to the limited antenna separations, it is common to have an undesired in-band signal of 0 dBm or more. The supposed GaAs FETs are actually bipolar medium power RF transistors. The canned filter nearby is probably a lowpass filter for the synthesizer DC output. The synthesizer appears to be a typical TTL divider type, with a high frequency pre-scaler.
@@alexander19681 I highly agree, non RF'ers commonly refer to it as "Magic". I enjoy RF and was smitten with a healthy interest in it at an early age. I suspect you experienced the same "ailment"?
Believe me or not, after watching this video, I went on ebay to check the item, considering to grab one of them.. and I checked the other things from the same seller. I found and ordered.... a satellite part 🤯! UV detector head for 1967 Ariel-3 british satellite ! Video about it on my channel in 2-3 weeks I hope, meanwhile I have done 2 posts about it.
i would love one of these, i would suss out every aspect of it & attemp to rig a controle panel to it & get it up for a test, i bet i could suss it given a few days
Yes, Berylium Oxide is used between the flange and die, it's one of the best known thermally conductive electrical insulators. For lower power applications Aluminum Oxide is used.
Most the time the army will just get rid of surplus in government auctions, opened to anyone... and then complain years later about their stuff being in the wild, like it happened a few months ago with a old missile fuselage found in some backyard in the US 😂
Thanks for this Teardown. This is a rack-mount unit that was likely used onboard an aircraft for UHF transmission
This looks like an aircraft communications transciever for the UHF aircraft band (225 to 400 MHz), probably designed in the mid 1970's. The power supply looks to be a linear voltage regulation drawn from a 3 phase power transformer. Switching power supplies were non-preferred due to the EMI they generate and high power bipolar switching transistors are relatively slow compared to FETs. The only problem is, I don't see any large bulk filter capacitors. You don't need that much filtering though with a 3 phase, full wave rectifier with a 115 volt, 400 Hz line.
The RF power amp (or transmitter) is linear and low level modulated using bipolar transistors. Those hybrid splitter/combiners may be the 90 degree type, which are used to isolate the parallel outputs for reduced distortion. My best guess on the output power is 100 watts CW, with 95% AM modulation capability. DC power needed for the RF power amp is probably 28 Vdc at 20 amps.
The receiver probably uses 3 pre-selectors to cover the broad frequency range. Using 3 pre-selectors also reduces the signal level across the varactor diodes, which reduces intermodulation distortion. On an aeroplane with multiple communication transceivers, due to the limited antenna separations, it is common to have an undesired in-band signal of 0 dBm or more. The supposed GaAs FETs are actually bipolar medium power RF transistors. The canned filter nearby is probably a lowpass filter for the synthesizer DC output. The synthesizer appears to be a typical TTL divider type, with a high frequency pre-scaler.
good explanation
@@alexander19681 Thanks, designing the RF and analogue portions of HF, VHF, and UHF aero comms was most of my career.
@@billharris6886 RF is a a very interesting branch of electronics that few people understand...
@@alexander19681 I highly agree, non RF'ers commonly refer to it as "Magic". I enjoy RF and was smitten with a healthy interest in it at an early age. I suspect you experienced the same "ailment"?
@@billharris6886 Correct.
Believe me or not, after watching this video, I went on ebay to check the item, considering to grab one of them.. and I checked the other things from the same seller. I found and ordered.... a satellite part 🤯! UV detector head for 1967 Ariel-3 british satellite ! Video about it on my channel in 2-3 weeks I hope, meanwhile I have done 2 posts about it.
I hope you will rebuild it again
i would love one of these, i would suss out every aspect of it & attemp to rig a controle panel to it & get it up for a test, i bet i could suss it given a few days
Does the RF power transistor contain dangerous beryllium?
Let's hope so.
Yes, Berylium Oxide is used between the flange and die, it's one of the best known thermally conductive electrical insulators. For lower power applications Aluminum Oxide is used.
@@billharris6886 we hope it is not more dangerous like the contents of a "pager"
@@deanagoes2791 LOL. #badbeeper
Tlenek berylu jest w srodku tranzystora
Удивительная схожесть схемотехники НАТО США СССР )))) Прям копия))) Прям мы не рабы и это все не театр))
It Out of a Mil Aeroplane!!!
not frountends! they are VCOs
Funny, ex-military components are supposed to be destroyed and not make it to the civilian marketplace 😮
Most the time the army will just get rid of surplus in government auctions, opened to anyone... and then complain years later about their stuff being in the wild, like it happened a few months ago with a old missile fuselage found in some backyard in the US 😂
It depends. It's pretty easy to buy ex Army radios in the UK as the encryption systems were seperate.
Piekny PA