On 2025-03-20 13:33, K9HZ wrote:
Yeah but¡ what¡¯s different? Did you:
* Play with wires
* Move equipment
* Change microphones
* Etc. ?
Well, I did recently...
Wire up an EHFW antenna. And a coax switch. The coax switch switches
between my existing trap vertical,
the EFHW, and the dummy load. The EFHW has a dedicated MFJ998RT remote
autotuner. The vertical has a
second dedicated autotuner. Each autotuner has its own bias T which is
past the coax switch.
The setup is: T41->Bigger Linear->LP100->Coax Switch -> bias-T -> Trap
Vertical
-> bias-T ->
common-mode-choke -> EFHW
HOWEVER, the fault is manifesting itself with the coax switch switched
to the dummy load. Also,
I tried bypassing everything and connecting the T41 direct to the dummy
load - no difference.
- Jerry, KF6VB
DR. WILLIAM J. SCHMIDT - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
PJ2/K9HZ VP2EHZ
Owner - Operator
Big Signal Ranch ¨C K9ZC
Staunton, Illinois
Owner ¨C Operator
Villa Grand Piton ¨C J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com [2]
Moderator: North American QRO Group at Groups.IO.
Moderator: Amateur Radio Builders Group at Groups.IO.
email: bill@...
FROM: [email protected] <[email protected]>
ON BEHALF OF jerry-KF6VB
SENT: Thursday, March 20, 2025 3:30 PM
TO: [email protected]
CC: K9HZ <bill@...>
SUBJECT: Re: [AmateurRadioBuilders] T41 high frequency weirdness
On 2025-03-20 12:19, K9HZ wrote:
What has changed?
*** Nothing!!!!!!!!!!!!!! That I know of. Well, obviously SOMETHING
has
changed, because it didn't use to do that.
- Jerry
DR. WILLIAM J. SCHMIDT - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
PJ2/K9HZ VP2EHZ
Owner - Operator
Big Signal Ranch ¨C K9ZC
Staunton, Illinois
Owner ¨C Operator
Villa Grand Piton ¨C J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com [1] [1]
Moderator: North American QRO Group at Groups.IO.
Moderator: Amateur Radio Builders Group at Groups.IO.
email: bill@...
FROM: [email protected]
<[email protected]>
ON BEHALF OF jerry-KF6VB
SENT: Thursday, March 20, 2025 2:09 PM
TO: AmateurRadioBuilders <[email protected]>
SUBJECT: [AmateurRadioBuilders] T41 high frequency weirdness
My T41 has started doing something weird on 15M and 10M. On 10M,
when
I
hit the mike button, I immediately get 6W out on my
Telepost 100LP - without talking into the mike!
I piped the output from the dummy load ( actually, a Bird 500W 30dB
attenuator ) into my Rigol SA. Signal at 28.350MHz looks reasonably
normal - carrier about 30dB down from voice peaks.
HOWEVER, when I increased the span, I found a giant spur at
33.305883
MHz. About 15dB taller than the proper output signal ( at 28.350MHz
).
If I go to 24.9MHz and transmit, the same sort of spur appears - at
32.305883 MHz.
If I go to 21.2MHz & transmit, the spur is at 27.9195 MHz. (
Telepost
says 2.7W )
If I go to 18.096MHz - no spur.
14.2MHz and below - no spur.
At a wide span, it looks like a nice clean peak. But if I crank down
on
it, it starts to get messy.
This is a latest-greatest V12, with the K9Hz BPF, LPF, and PA.
I connected the output of the RF board directly to the SA - no
constant
spur. Plenty of harmonics with no BPF or LPF though.
I can only conclude that the PA is oscillating:(.
As to why it doesn't oscillate on lower bands....some interaction
between the PA and the BPF & LPF?
- Jerry, KF6VB
Links:
------
[1]
[2] /g/AmateurRadioBuilders/message/6210
[3] /mt/111814954/243852
[4] /g/AmateurRadioBuilders/post
[5] /g/AmateurRadioBuilders/editsub/243852
[6]
/g/AmateurRadioBuilders/leave/11522011/243852/920863695/xyzzy
Links:
------
[1]
[2]
[3] /g/AmateurRadioBuilders/message/6221
[4] /mt/111814954/243852
[5] /g/AmateurRadioBuilders/post
[6] /g/AmateurRadioBuilders/editsub/243852
[7]
/g/AmateurRadioBuilders/leave/11522011/243852/920863695/xyzzy
