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1/2 watt from Cyrn-y-Brain


#1

I did a quick activation of Cyrn-y-Brain NW-043 on Sunday. A very simple setup… handheld and a J-Pole made from twin feeder up a fishing rod. I was going to concentrate on 2m FM but I had the option of 70cms FM and also 2m/70cms D-Star. In addition I took my 23cms handheld and remembered to take a battery for it this time. (c.f. Lambrigg Fell and Gerald’s Goating activation!)

I decided to run my Icom IC80AD handheld on low power so the battery would last and I thought I was running 1W. As it was the output was set to 1/2W. I still was able to work 22 stations around the NW of England. Now from previous VHF contesting experience, I know that Cyrn-y-Brain is a good location but I was very pleased with how well such a low power worked especially considering the simple antenna and the fact there’s a 5m of RG-174 to add to the loss.

To round off the day nicely, I was able to have my first contact with Simon M1AVV who was just across the way on Foel Fenli NW-051. Even better we did our summit to summit on 23cms FM. This was Simon’s 1st S2S on 23cms. OK, it was no real DX but still put a smile on my face. I think I might invest in a 4m handheld for when I get down this way again so I can join in the action there.

A very enjoyable activation, thanks to all the chasers who called. The Ponderosa was mad busy still at 4pm and there appeared to be an original Jaguar SS 100 in the car park. They have such a silly price tag these days I was really surprised to see one being on the roads.

Andy, M0FMF
(/P in IO83)


#2

Andy,

Your 1/2W works well from a good Location, it was nice to work you whilst I was operating as GB0GWR on 2m FM in Cheltenham (144 Km).

Stewart G0LGS


#3

In reply to G0LGS:

You were a very good signal Stewart and I was pleasantly surprised to be able to work you for such a simple setup at my end.

I had some more QRP fun on the way home yesterday. Calling in on Winter Hill SP-010, I parked at the end of the public road and walked up to the top. I sat on a concrete block to keep dry and was just out of the cloud.

Using my Icom IC-80AD (2m/70cms) with its supplied rubber duck or my Icom X-21AT (23cms) and its rubber duck and a 3S1P LiPo battery I worked the following:

2m: 9 stations using either 0.5W or 2.5W
70cms: 3 stations using 0.5W
23cms: 2 stations using either 0.75W or 0.1W

ODX was G3SMT in Oswestry at 100kms on 70cms and 0.5W.

Nipping up Winter Hill was an excellent way to break up a tedious 4.5hr drive home. Another unique, another point and QSOs on 3 bands using nothing more than a handy and its own antenna. Simple yet very rewarding.

Andy
MM0FMF


#4

In reply to MM0FMF:

Hi Andy!

Would you care to quote the dimensions of your 2m J-pole? Are you using the heavy-duty black slotted twin feeder to make it?

73,

Walt (G3NYY)


#5

In reply to G3NYY:

I got them from someone’s website via a Google search. However, I will measure it tonight and post my dimensions because the 1st one I built would not resonate on 2m. It turns out there was a metric / imperial conversion error on the website I referenced. When I checked a few more sites I found several with concurring dimensions. I didn’t use ladder line but the thin lightweight 300Ohm twin that is typically provided for use as an FM antenna with hifi tuners. ISTR I got it from Maplin at horrendous cost but I was in a hurry.

Andy
MM0FMF


#6

In reply to MM0FMF:

See http://www.qsl.net/dk7zb/J_Pole/wiremanjpole.htm and search for his 2m measurements and diagram. I have the following lengths for my version.

A = 130cm
B = 42cm
C = 3cm

My gap is only 5mm not 10mm.

I used the transparent 300 ohm flat twin feeder from Maplin and feed with approx. 5m of RG174 (quite lossy). It’s built as per the website but with my lengths. Hanging free in the shack from a light fitting with the feeder partly coiled and partly draped over the junk in here, my MFJ259B says

145.5MHz SWR=1.3 R=63 X=5

I think I made it the length in the article originally and trimmed it a bit. I wanted a lightweight backup antenna for VHF as the 817 and rubber duck was not up to the job in Scotland, a better antenna was needed most of the time due to lower population density and less flat areas.

The SWR can be finicky! I normally attach the top of the J-Pole to the top of my fishing pole and attach the bottom of the twin feeder to the fishing pole with a double sided Velcro strap. The feeder is allowed to hang free and terminates in a BNC plug. I have a 1m(ish) length of extra flexy RG58 that has an SMA male on one end (W.H. Westlake) and a BNC cable end female. This gives me the ability to use the FT 817, VX 170 and IC-80AD with the antenna. The 817 seems to often get RF feedback problems and I think a ferrite choke on the microphone cable is needed on mine on 2m. I have issues with the rubber duck on the 817 at 5W, might just be my 817 though. No problems observed with either 2m capable handheld.

Slightly OT: the VX 170 is better in high external VHF RF fields than the IC-80AD. There was some QRM/desense on Cyrn-y-Brain with the IC-80AD that I’ve not seen with the VX 170. No problems observed from near the main mast cable anchor on Winter Hill using the IC-80AD, so 700MHz RF (and many dBW of it) doesn’t affect it!

Andy
MM0FMF


#7

In reply to MM0FMF:

Many thanks, Andy! I’ll give it a try.

73,
Walt (G3NYY)


#8

Hi Andy,

I saw you spotted for Winter Hill & took a listen for you on 2m from outside my office quite high up in Blackburn, but although I could hear Mike GW0DSP (Under his other callsign) working you, I could not hear you on my VX7R unfortunately. Although I have a good view of the top half of the main Winter Hill mast, the bottom half is screened by Darwen Moor.

It would have been nice to work you on 2m for a change :wink:

Hi Walt,

I also contructed a J-Pole for 2m using the tranlucent 300 Ohm ribbon feeder from Maplin. I based my dimensions on the amended dimensions of the 4m version as featured on Summitsbase. I have been told off before for not crediting the originator of the modified dimensions but I think it may have been MW0IDX, I could be wrong though.

I built the 4m version first & it worked perfectly first time with 1:1 SWR in the FM portion of the 4m band, easily handling 40 Watts (my maximum on that band). Following its success on 4m I scaled the dimensions for both 6m & 2m, both versions of which also worked first time.

I did take some photos during the construction of my 2m version with the intention of adding them to Summitsbase, but as with many things I do, I haven’t got around to it yet.

I have now though uploaded the photos & a schematic diagram to my Flickr account & you are welcome to take a look at them. My dimensions are slightly different to Andy’s but knowing of several people who have had wildly different results when using exactly the same dimensions, that does not surprise me. My J-Pole has the top & bottom ends of the 300 Ohm ribbon soldered together, but you could use a single conductor above the matching section though this may change the dimensions.

For years I avoided J-Pole antennas simply because coming from an electrical background I saw the feed method as a dead short & didn’t think it would work. Of course RF is different to AC Mains & I now have no hesitation in recomending them as cheap, reliable & very portable antennas for 6m upwards.

Best of luck with your 2m version, let us know how you get on :slight_smile:

My dimensions & a couple of photos are below, of course the relevant parts were waterproofed with Insulation tape before use. Heat shrink PVC would probably make a neater job.

Look at that soldering, you wouldn’t believe I used to do it for a living HI!

Here is one of my favourite photos showing the 4m version in use on G/SP-007 Fair Snape Fell back in March.

Best 73,

Mark G0VOF


#9

In reply to G0VOF:

Your antenna is a Slim Jim rather than a traditional J-Pole. The Slim Jim was a development on the J-Pole by the late Fred Judd G2BCX. The J-Pole doesn’t have the short across the top end and the big gap.

I can’t remember the claimed differences between the two though Mark. Both work, cost next to nothing to make and are lightweight and simple.

Andy
MM0FMF


#10

In reply to MM0FMF:

As neither is an antenna I have really used until recently I am happy to call with it by either name :wink:

They are cheap, portable, easy to make & more importantly, they work!

The true (Single conductor) J-Pole would make a better backpack antenna whilst “on the move” as a single stiff whip would be easier to mount than ribbon cable, but for static use lashed to a pole, I doubt that there would be any difference in performance.

Slim Jim or J-Pole, either way, a good omni-directional, vertically polarised antenna. Ideal for 6m/4m/2m FM SOTA :slight_smile:

73,

Mark G0VOF


#11

In reply to G0VOF:

Many thanks for the info, Mark. I’ll have a browse at your web pages.

73,
Walt (G3NYY)