Output power on different bands

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DB8GK
 

Posts: 4
Joined: 02 Jun 2022, 12:42

Output power on different bands

Post by DB8GK »

Hi all,

I recently received mt (tr)uSDX, ordered from the AliExpress UpTech store.

I hooked it up to the audio interface of my laptop, using nothing but straight cables, and then used the tuning feature of JTDX to generate a signal. This was sent through an ATU-100 antenna tuning unit for power measurement, into a dummy load. The (tr)uSDX was powered with a 12V USB-C PD trigger module.

Here's the result of the measurement across the bands:

20m: 1.9W
30m: 3.0W
40m: 1.7W
60m: 2.0W
80m: 3.5W

My questions are: Are those typical values? Is especially the huge difference between power output on different bands to be expected? Would I see higher power outputs by supplying more voltage? Might my audio level be too low to achieve the theoretical 5W output, and is there something in the configuration I can tune?

73 de Andreas, DB8GK
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DH2LAB
 

Posts: 51
Joined: 08 Mar 2022, 01:39
Location: Kiel
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Re: Output power on different bands

Post by DH2LAB »

The device is pre-assembled and not really adjusted.
Use this guide:

https://www.youtube.com/watch?v=qN7hHsvcNMM

viewtopic.php?p=1686#p1686

Normally you have 4-5 W at 12V if you tune the toroids properly.
73 de Matt, DH2LAB
DB8GK
 

Posts: 4
Joined: 02 Jun 2022, 12:42

Re: Output power on different bands

Post by DB8GK »

Great information, thanks!
Luca66
 

Posts: 123
Joined: 16 Apr 2022, 13:02

Re: Output power on different bands

Post by Luca66 »

By following the coils spacing adjustment on the toroid you may get a benefit, but you may need to add or remove a coil.
on6uu
 

Posts: 4
Joined: 03 Jan 2022, 04:50

Re: Output power on different bands

Post by on6uu »

how safe is it too unsolder the toroids ?
72
ON6UU
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DH2LAB
 

Posts: 51
Joined: 08 Mar 2022, 01:39
Location: Kiel
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Re: Output power on different bands

Post by DH2LAB »

on6uu wrote: 05 Jun 2022, 12:17 how safe is it too unsolder the toroids ?
If it smells like fried finger, you should practice it first. :lol:

Good soldering skills should be available anyway.
And if you boil out the solder lugs, you've done something wrong. :!:
73 de Matt, DH2LAB
LU1DLP
 

Posts: 3
Joined: 12 Jun 2022, 22:37

Re: Output power on different bands

Post by LU1DLP »

Power input is very important. In my rig in 40m with 11.6V power is 4,5W and with 13,8V increese to 5,5W
karmeluk
 

Posts: 1
Joined: 09 Sep 2022, 19:22

Re: Output power on different bands

Post by karmeluk »

Please tell me what is the maximum power input: Volts / mAh?

Thank you,
Boris
HB9HJF
 

Posts: 31
Joined: 29 Aug 2022, 16:43
Location: Zurich, Switzerland

Re: Output power on different bands

Post by HB9HJF »

Theoretically should still work with ~15V; I'd try not to put more than the standard 13.8V into it to keep within the safety margins available.
-- Cathal Ferris.
Paddler, pedaller, stargazer, nerd.
Wiggler of electrons both in silicon and in the ether.
VA7RLX
 

Posts: 9
Joined: 20 Oct 2022, 21:36

Re: Output power on different bands

Post by VA7RLX »

I too am seeing the same issue with a pre-built unit ordered from uellyqh (Sunny) on the eBay "official vendor" page. No criticism of this vendor - they have been incredibly helpful.

I'm using a power supply built with 8 AA cells. Currently measuring 12.12V on no load.

My power output on 40m is 3.2 to 3.4W and on 20m is 5.4 to 6W. A huge difference. SWR on the antenna is about 1.3

This is measured on the internal wattmeter and I have no idea how useful that is. I bought a used QRP wattmeter but it doesn't work! Wildly inaccurate!

I'm newly licensed and brand new to QRP. Any comments useful. I gather it may be a tuning issue on the RF board?

Tnx VA7RLX Ritchie in BC, Canada
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