High Band no output power/receive

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VA3SPN
 

Posts: 4
Joined: 06 Dec 2023, 01:17

High Band no output power/receive

Post by VA3SPN »

I have Just finished building my High band (tr)usdx kit. I have uploaded my firmware as per the instructions and edited the band selection to high band.

My concern is that I have very low (0.02W) output on any band. The radio does however measure the swr of the antenna/dummy load reasonably accurately. I also have no receive, even when testing at ft8 frequencies I have nothing on any band. I have tried my other prebuilt (tr)usdx on 20m and it receives the ft8 signal at at least s8 where the high band one hears nothing. I have done some quick checks with a multi meter from the sma connector to the swr toroids, as well as verifying connection between the two boards and all that checks out ok. I do not have any fancy test equipment (multi meter and a nano vna are about it) so I'm not sure where to go first with as far as testing the radio.

Thanks in advance for your help
VA3SPN
VA3SPN
 

Posts: 4
Joined: 06 Dec 2023, 01:17

Re: High Band no output power/receive

Post by VA3SPN »

So I've had some more time to check into this and have rechecked continuity between al the toroids and the board. everything there seems ok. I have reflowed every solder I made on both the main and rf board for good measure.
The relays are clicking when changing bands, and I have continuity between the appropriate relay pin and the rf pin on the rf board/mainboard.
I compared the placement of the toroids to my preassembled low bands (tr)usdx and they are layed out the same.

I still have not come up with any reason why this radio has no tx power out and no receive.
dl6sez
 

Posts: 399
Joined: 30 Dec 2021, 22:54

Re: High Band no output power/receive

Post by dl6sez »

Hello OM,

check T1 and T2 windings and connection points, compare with your working low band.
Check SMA connector soldering, often a problem too.
Another thing: don't tx if your rx path doesn't work! You probably already killed your FDT86256 FET....
If rx works and you found the reason, for tx also don't forget to adjust tx bias to 160 in menue.
No other idea, but when rx doesn't work you could have killed maybe more with your txing without a working path to antenna! Check Q1 rx mute in circuit.

Interchange the PA board to the working (tr)uSDX and check it there....

73 de Chris
Chris DL6SEZ, JN48XL near Ulm, Southern Germany
VA3SPN
 

Posts: 4
Joined: 06 Dec 2023, 01:17

Re: High Band no output power/receive

Post by VA3SPN »

Thanks for the replies,

I did a quick continuity test on FDT8625 and it had shorted. I replaced it, and still had no receive. I was able to swap boards back and fourth and found that the issue was in the PA board. Everything looked decent on the board. In the past I had come across a post about issues with C7 on the PA board, so I reflowed the connections to that and I now have proper receive and transmit.

After a quick verification of settings and an alignment and I had it on the air!
vk2tty
 

Posts: 26
Joined: 26 Nov 2023, 06:35
Location: QF57UC, Australia
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Re: High Band no output power/receive

Post by vk2tty »

VA3SPN wrote: 23 Dec 2023, 20:46 After a quick verification of settings and an alignment and I had it on the air!
Success!
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