1 Pole Short of a Rhombic - G/SP-013

Activation Reports
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On looking at the weather forecast , it was decided on Friday evening between myself and Peter (M1BZJ) to head to G/SP-013 Gun for an activation on Saturday 17th Sept. Due to the nature of the summit being large, flat and an easy walk in, rather than taking lots of radios, we took lots of wire (I have about 5km of wire on rolls picked up as part of an ebay job lot). We took 2 rolls of 100m.

Peter wanted to try out his FT-891 on a summit and I took my dual band handie (just in case). We had about 170m of wire on rolls in order to construct different antena while on summit.

We decided to leave the tuner capable of top-band in the car since we thought (incorrectly) it would be fruitless during the middle of the day. Turned out MW0PJE/P on GW/NW-043 was trying top band.

Mostly used some variation on a vertical antenna - a 1/4 wave for 40m with radials which also tuned up on 15m , 1/2 wave for 20m with a 49/1 UnUn. Both worked well, and having 100W also helped. Early afternoon a 1/2wave vertical for 10m was constructed and spot was placed. The band was semi-open with quite a bit of QSB but the antenna worked well, with 3 stateside, 2 Turkish and a Brazilian in the log with 5x reports both ways.

I was impressed with the ft-891. The only downside is the lack of VHF/UHF capability. The receive audio was good and the menu system was more intuitive than the 817/857. Other than the notch filter (used once) the DSP wasn’t required for any QSO. I did need to stop once on 20m while running a pile up on 20m as my voice went, sorry if anyone missed me but I needed liquid sustenance.

Later in the afternoon, I wondered about building a rhombic antenna. Why? Because we could. Unfortunately we were one pole short for the supports , but the idea is now in my head to try next year. Whilst they are not the super hi-gain antenna of legend, they do offer some advantages if you have the room. They are multiband (with the help of a tuner). On a long all-day activation, you could rotate them for the desired paths. And they sound impressive when you mention them in a QSO :slight_smile: We might need to practice the construction off summit to get the setup right before deploying in anger. Some method of determining the angles between the legs (whilst not super critical) would be needed.

Good to see Tom M1EYP appear on summit, who was also trying out a new antenna, but I’ll let him report on that one :). Also his comment of “If I’d known you were up here, I wouldn’t have come” could have been taken two ways :laughing: Fortunately, I knew how it was meant.

38 QSO in total in an odd symetry of. 19 Summit to Summit - 19 Non summit to summit over 19 DXCC. 34 on HF (various bands) SSB and 4 on 2m FM. Map below

SP-013
SP-013831Ă—646 90.9 KB

Ian

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If your wires are pre-cut to the right length, and you carry a tape measure, the angle takes care of itself. I’m in the process of installing a North America 40 mtr rhombic at my home QTH, and other than using a compass to get a rough idea where my signal might go, the 100-mtr tape measure carries the day…
73
John

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3

That sounds like the most simplistic and therefore ideal solution to me too.
Fortunately, we have the use of a field we can drive to for testing purposes too. So over winter will try to put something together that can be deployed on a summit. I was thinking a long piece of string or wire measured to the correct distance to give the spacing between the feedpoint and opposite pole with the cut length of wire taking care of the angles. The same implementation as yours with a little less weight of a tape measure.

Ian

4

Short of that, you still had the necessary for a V-beam!

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I thought conditions were “up” quite a lot on Saturday when I worked you on 40m Ian. Lots of UK stations and I was getting lots of 59 reports for the inverted (sloping) L EFHW and 10W. Signals on 20m CW were strong but ODX was Fred KT5X on 15m CW at 7400km using the same antenna.

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I was short of the necessary knowledge :slight_smile: To be honest, I didn’t know it was a thing until this morning when I was looking up information on rhombics.

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Yes, I agree. Across all the bands the signals were pretty good. For some reason, we didn’t spend much time on 15m preferring to jump straight to 10m. Did check on 6m too but nothing happening there.

Good to get you in the log though on 40m.

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Couldn’t you get Tom to hold that corner?

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Unfortunately, Tom had a prior engagement with Macclesfield Town vs Buxton in the FA cup. Good thinking though :grinning:

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Local derby … 2-0 Macclesfield, so I would guess Tom’s happy :slight_smile:

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Actually, the distance across the midpoint is better (and less string to carry!). I should have edited my first comment to say “wire pre-MEASURED” (not cut), since, of course, you don’t cut at the midpoints.

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I tried a 40M loop once on a summit - was kinda of PITA as the summit I picked barely had the room. But only required one support pole and gave me 40, 20, 15, and 10M with decent enough performance. I’ve always wanted to try a Rhombic since we used them in our military daze :wink: I fashioned the 40m loop after an article I read years ago titled “A one masted sloop antenna” or something to that effect in QST mag…Maybe iffen I get the chance I’ll look for that article…

73, Todd KH2TJ

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I thought it was a derogatory term for a clueless radio amateur??

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