Apologies Andy, yep I got the correct end of the stick but just worded my post a bit oddly. As you rightly say though, the AST sets precedent (with curbs) but there’s worse out there. Not to mention all the vultures circling for whatever chunks of allocations they can prise away.
An HF one of recent interest was the FCC approval for encrypted financial transactions to be tested. I’m unsure what the outcome of the tests was - as in, has it been approved permanently - but it’s an interesting use case.
Exchanges in New York, London and I think it was either Chicago and/or Toronto were testing sending encrypted market transaction data over HF. Why, when there are undersea links, overland infrastructure and all the rest of it (setting aside Maritime and critical infrastructure risk here for a sec)?
It comes down to the maths. I forget the exact formula and digits, but it’s something along the lines of sending the transaction data over HF is fractionally faster than sending digital data down a wire. Probably less than the blink of an eye, but there is still a measurable difference. Then when you weigh up that difference and stick a monetary value on it, those fractions of a millisecond (or whatever the maths works out to, I forget, there’s an article I read about it somewhere that goes in to more detail, plus the FCC papers to read) could mean a monetary value of millions (possibly even billions ad infinitum).
In fact the past few times up Billinge Hill I’ve not done 2m at all except for the occaisional summit to summit.
Having said that, refer to my previous comments about being in the NW England and having large conurbations nearby. Its probably a lot harder on remoter summits.
The fun comes when you get a reply on 2m having called on 70cm when they have a dual bander monitoring both calling channels and assume you are on 2m
I’ve had some success by calling in to the void. That said, if I start on 2 meters, if it’s not super busy and if I am on the RH-770 I might say does that person wish to try 70cm if they can do so on their side. I’ve had a lot of success that way as it’s just a quick flick over to UHF and either you’ll work them or not.
Failing that I usually make a mention during working stations that I will move to UHF afterwards. Just to give the heads up to anyopne listening that I will try 70 as well. That works quite well too as I find I get positive responses that the other person is pleased to hear someone else wants to work 70cm too.
If I am not on the RH-770 or the 270 Moxon (in other words I’m on the 2m Slim G), then I’ll just make mention that 70cm will follow after I’ve finished on 2m. Just drop it in to the QSO what hardware I am running - so they might know I’ve to switch things around - and folks get the heads up then that it’s coming down the line later on.
See us 70cm fans are lurking out there, we just need to make UHF more glam!
Apparently, it’s high-frequency trading firms - and not major market exchanges like New York & London - that have built private shortwave networks and are aggressively lobbying regulators like the FCC to secure international bands for encrypted data transmission. It seems a trade between Chicago and London via shortwave shaves 10-15s off the existing trans-Atlantic fibre connections.
They send the trade simultaneously via HF and submarine cables. If the radio one gets garbled (due to the ionosphere not playing ball) they still get the trade through, and mostly the HF one will give them a competitive advantage – a so-called ‘indeterministic speed booster’.
Although HFT firms would be using commercial HF bands (not amateur ones) the ARRL are voicing fierce objections due to the very high power used (up to 20kW) and wide bandwidths. They suspect the previously flagged and logged unidentifiable, wideband data bursts heard on the 20m band are due to these trial transmissions.
When I came back to ham radio in 2003 (after moving QTH and taking time off to raise a family) I had no gear and no shack, and for a quick start got an FT817. Having no antennas, as a temporary step while getting beams and rotator I built a Slim Jim. This was nominally a 2m antenna but I soon found it worked very well on 70cm - being 1.5 wave on 70cm it probably wasted some power warming clouds, but it got contacts. Give yours a try on 70cm, it may surprise you!
A half wave dipole is also resonant on 3 times its base frequency. So a 7MHz dipole can also be used on 21MHz, for example. A slim jim is a half wave dipole end fed via a matching stub so if it’s resonant on 144MHz it will also be resonant on 432MHz.
In practice it isn’t quite as simple as this due to end effects and probably other things too. But often an antenna works well enough to take advantage of this.
An EFHW is resonant on all multiples of its frequency. So a 7MHz EFHW can also be used on 14MHz, 21MHz and 28MHz. Since a slim jim is end fed perhaps this applies here too.
They can be pressed into service, but not ideal - although the radiator is near resonant, I guess the tapping point on the matching stub is not optimal for 70 cm.
I tried six a few times but no joy. I did get DL8MEK/P (DL/CG-059) on ten, though the QSB was pretty fierce, so I was probably on the edge of the reflection.
Today during my activation of G/NP-028 I tried my 2m antennas on 70cm.
The vertical flowerpot antenna showed a few bars on the FT817’s SWR meter at 433.500MHz but the rig was happy and I worked 5 stations. I’m sure some of these saw my spot on Sotawatch but I think a couple were chance contacts. It seemed to have a better SWR at 432.200MHz but I got no QSOs on 70cm SSB.
The horizontally polarised hourglass showed a lot of bars on the 817 SWR meter so I decided not to try it on 70cm. It may have worked fine but I have no idea what the SWR scale is. There is nothing in the manual that I could find that explains this. Perhaps as long as the rig lets me transmit its OK.
I used an external SWR meter with my 817 and 857 when I first got them. When it showed 2:1 there were four bars showing. It isn’t safe to take this as definitive but its a useful indication.
I tried my roll-up J-pole on 70cm a few times; it was rubbish.
By contrast my Diamond RH770 is excellent on 70cm. With one S2S [so not statistically significant] I had both 2m and 70cm QSOs with the same op in short succession and the 70cm QSO was stronger. I can’t say it was definitely due to the RH770.
I think the higher gain of my RH770 on 70cm (5.5 dBi) compared to 2m 3.0 dBi) did not outweigh the higher free-space attenuation on 70cm. So, maybe in this case it might have been due to there being more refraction and reflection opportunities at 433MHz in mountainous areas .
I had a look at those pages soon after posting. The gist is that the FT817 SWR meter doesn’t read SWR but reflected power. So at lower output power settings you will always get fewer SWR bars than at higher output powers. Also, the calibration is way off so it can only be a relative guide.
That’s designed as a dual band antenna (there’s a loading coil in the middle) whereas I was trying a 2m antenna on 70cm.
