The new Index QRP+ has been daring me to measure its spectral output - and the ULTRA's latest firmware supports storage of the displayed traces as a bitmap file, saved to an included 32GB MicroSD card.
A combination of Elecraft's bi-directional coupler and my step attenuator knocked its 10W output down by 40dB, to 1mW.
For some reason, I saw no harmonics on 160, 80 or 40 meters so I brought out the big (comparatively) Rigol. Same thing - and something I need to investigate. Surely, there are harmonics being generated on these bands...
Incidentally, I looked at the other bands on the Rigol as well - the displayed traces were practically identical to those of the tinySA ULTRA.
So why buy a Rigol instead of the tinySA?
Two reasons: 10Hz minimum RBW, much faster scan times for a given RBW and the Rigol has a built-in tracking generator (this allows it to perform some of the functions of a VNA).
However, my (absolutely mint) Rigol is for sale ($700 shipped, US only).
But on to 30 to 10 meters on the QRP+:
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No so great on some bands...
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You must be going to upgrade... Good price on that Rigol, I've been mulling an upgrade to their 3Ghz model.. Been a fantastic SA... 73
ReplyDeleteBelieve it or not, the tinySA Ultra is sufficient for what I want to do. I don't need to look above 150 MHz (the 5th harmonic on 10m) and I don't need 10 Hz RBW. Sacrilege, I know - my old self would be surprised at my new self!
Delete73,
John
I have both the 200W and 2KW Elecraft HF couplers, for use with my P3. It never occurred to me that I could use them with my bench equipment, which includes a Rigol. I had home-brewed a coupler that wasn't all that flat, so that I could do harmonic measurements for our Field Day rigs, as requested by the airport radio officer. Can you point me to some online resource that would help me figure out how to use the Elecraft couplers? Thanks.
ReplyDelete73,
-- Dave, N8SBE
Hi Dave, the coupler I used here was the CP1:
Deletehttps://elecraft.com/products/cp1-directional-coupler-kit
It's one of Elecraft's minor kits and a very useful one.
https://elecraft.com/collections/test-equipment/products/cp1-directional-coupler-kit
It can be built to provide either 20 or 30 dB of attenuation and can handle a 200W input if built for 30dB. I'm afraid I don't know anything about the couplers you mentioned and the Elecraft website doesn't provide much info:
https://elecraft.com/products/dchf-200_1-8-54-mhz-0-1-200w
Do you know what the output level is with a given input? I'd sure like to see a schematic before suggesting to anyone that they should use it apart from what it was designed for (the PX3 I think?). Someone on the E reflector could probably tell you if this application is possible with these couplers. But do look at the CP1 - it's very handy and gets little mention...this surprises me given the popularity of the tinySA.
73,
John
The CP1 looks interesting, but I needed something flat to at least 250 MHz, so that I could read the harmonic content up into the local airport frequency band. Seems like the one that WB7OND posted below may fill the bill. If I can get one that's flatter than the one I have, it will be very useful. The one I have requires me to calibrate the Rigol since the response falls off by several dB at the low and high ends, so I lose some dynamic range in the measurements in those areas.
DeleteThose couplers sound like the couplers for Elecraft W2 power meter... https://elecraft.com/products/w2
ReplyDeleteI built one of these with good sucess up to about 144Mhz https://ae6pm.com/SCCARA-GRAM_Articles/A_40_dB_Power_Tap.pdf
40db puts my 100w in range of my smaller fixed attenuators.