Tuning on the activator frequency before chasing!

I would imagine tuning this puppy up on your frequency would give you some grief.

(That’s a Bird43 showing full scale with a 25kW slug)

Hola Guru. Entiendo que estas cosas vuelvan loco a más de uno (yo directamente me enfurezco!) pero a mi parecer no es buena consejera el ¨escrache¨.
Creo que no hay necesidad de publicar el callsign del supuesto ¨infractor¨, simplemente porque estamos hablando de un ¨supuesto¨.
Saludos cordiales!

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This comes up from time to time on SOTA threads often as an argument as to why you don’t need an ATU. It’s only true for practical antennas like dipoles if you operate in a narrow range of frequency, e.g. on 30m band. If you look at the VSWR plot for my portable 80m half-wave dipole, you would want to tune up at each end of the band if you run QRP as I do.

To put some numbers to it, a typical 80m dipole has a bandwidth of about 170 kHz between the 2:1 points. This is a variable depending on the diameter of the wire (inter alia) but to cover the whole band the “wire” would have to have a diameter of nearly a metre! Still, a tube output stage with a pi tank will cover the whole band without trouble…:wink:

It’s not an issue for activating.

It is on 80m if you want to do both CW and phone, particularly if you want to try the DX window or the WAB frequency as well as CW.

Independently of whether we use a resonant antenna or not and we thus we need to use an antenna tunner, what it’s clear is we should never jump onto the spotted frequency of a SOTA activator we want to chase and tune up on top of everyone at that very moment. This is the subject in this thread.
However, let me inform you of some of my findings after a quick investigation this morning:

1- I believed I had chased Fabio on 7.034, but I didn’t, as he logged EA2CP instead. EA2CP and I were in skip yesterday on 40m so we were unable to hear each other and he may have gone on top of me after Fabio came initially back to EA2IF. I’ll delete my QSO with Fabio on 40m. Its great that I chased him again on 30m because I’m in the log this time.

2- The tuning on the frequency station I copied as F8DGV is not in Fabio’s log, but he logged F8DGF instead at about that same time. F8DGV doesn’t apparently exist as a valid licenced ham according to the info provided by Éric F5JKK and the info at QRZ.com.

3- F8DGF does exist and does participate in the SOTA program. Despite the fact that he recorded several SOTA chases in 2005, 2006, 2007 and 2008, but he has not loaded a single chase to the database since August 2008, I have him in my log as he chased me on 3 of my SOTA activations in 2018 (1) and 2019 (2), so it looks like he is still an active chaser in these days. I may have made a mistake when copied the DGV suffix or a mistake was made by himself when he first sent it, which is when I copied it, not paying further attention during his QSO with Fabio.

Best 73,


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A sweeping statement, Andy, with no explanation

You can see from the VSWR plot (I linked to) for my portable 80m dipole made from thin lightweight SOTAbeams wire that it has a bandwidth of 250kHz and has a VSWR of 2.6 at 3.800kHz. That means 20% reflected power compared to virtually zero at the resonant frequency.

More of a practical issue for me is my reluctance in winter weather to take and erect my 10m pole and quad-band linked dipole for ‘nearly resonant’ operation. When it’s howling a gale, I’ll rather throw up my tri-band EFHW and let my KX2’s ATU tune up on a band it wasn’t designed for.

When I go activating, I do not need to operate on all bands, all frequencies and all modes. I need to operate in some parts of some bands. I don’t flit from calling CQ SOTA on 20m SSB ( above 14.270 ) to trying to chase someone on 630m or 24GHz. A few bands covered adequately enable successful activations.

That’s a strawman argument, in fact, it’s absurd [so much so I suspect it’s a FMF wind-up]

Brian made a perfectly reasonable case that one might want to activate on 80m CW and SSB, or in my case, use a compromise antenna.

You might activate in a way that means your antenna is always resonant and don’t need to tune up. But you didn’t qualify your original emphatic statement so expect someone to challenge it.

I have an 80m antenna that demonstrates acceptable match on CW and SSB, not the full band, but it covers top of CW and bottom of SSB.

I have used it work CW and SSB stations on 80m on SOTA activations.

I do not have an issue that I do not have 1:1 match across the full band when activating.

No I cannot use it to chase in the DX window. But that raises two subsequent points

  • When I am activating SOTA, I AM THE DX

  • In the middle of the day, on 80m with a low slung dipole and QRP power levels, just what mystical DX am I seriously going to chase?

So I think Brian’s argument is the strawman.

Flat SWR from DC to daylight is not an issue especially when expectations are set to realistic not wishful.

EDIT: So I don’t need to tune-up on top of any ongoing QSOs.

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Groannnn… ever wished you hadn’t posted something on this Forum…


My 40 - 6m End Connected Windom does not need re-tuning on 40/30/20 when used with the KX2 and internal ATU:

The SWR varies from 2:1 to 4:1, as there is no impedance transformation with this type of Windom. Nevertheless, the KX2 handles it no problem; press ATU once (not on the activator’s QRG) and forget about it.

   73 de OE6FEG

Yeah…I thought the thread was about Guru’s statement above. I’ve experienced many operators tuning up on my activation frequencies…during my activation! Now, I do realize that some of the stations doing that may not hear ME (QRP) but for them not to hear the pileup of stations? Seems not very likely…

I like to keep an open mind regarding my fellow ham radio operators…but it’s hard to do sometimes. Just sayin’…

73, Brad

Some of the more prolonged tuning up incidents are possibly the pathetic wierdos that like to QRM activations, they unfortunately are always with us.

Yeah…I suppose you’re right Brian. Perhaps a sad reality…

73, Brad

We have a perhaps unique problem in VK: Because there is still a lot of commercial HF SSB traffic, there is a lot of commercial surplus SSB gear on offer. When used with the bespoke ATU, these things invariably re-tune EVERY TIME the CPU detects a frequency change, however small. I don’t own such a beast, but I’m told there is no way to defeat this “feature”. Curious, as our amateur regulations clearly state that our first transmission must always contain call signs. Not sure what the commercial band regs state - probably irrelevant, as compliance monitoring in vK is now at an all-time low.

It’s very possible these culprits are doing the on-frequency QRO tune-up and ‘riding roughshod’ over others patiently waiting in the pile-up, not out of ignorance of the protocols, but as a perverse pleasure. There’s a saying in the north of England “There’s nowt so strange as folk”.