Other SOTA sites: SOTAwatch | SOTA Home | Database | Video | Photos | Shop | Mapping | FAQs | Facebook | Contact SOTA

Great Orme GW/NW-070 Quick Report


#1

Well, I had a meeting arranged for today, with one of my suppliers in Gods wonderful county …Wales. This, of course, meant a nice opportunity to take in a summit on the way home. As I was driving past Llandudno on the return journey, Great Orme GW/NW-070 beckoned.

Arrived at the trig point at about 1230z and started to assemble the collinear, only to find I’d left the antenna clamps, back at the club shack. Doh!

All was not lost though, as I found the clamps for the Antron 99 in the car and with a quick bit of improvisation…Bingo, collinear up and running.

Self spotted, turned the rig on and as expected, found the most diabolical QRM from the radio masts. I decided to persevere and work my way through it, not easy though, as just about half of every qso was wiped out. I decided to take a look at 70cm, however, this was even worse and totally unworkable.

I took the liberty of taking a quick look at the qso scores for this summit on my mobile phone and was not really surprised to see the average number of qso’s per activation on 2m is just five :frowning:

Nevertheless, I pressed on and stuck it out working solely on 2fm after failing to find a single contact on 2m SSB.

Finished up with with 64 contacts including five into Cumbria. Worked two chasers, who had never managed to work Great Orme before and Dave M3XIE, who had only managed it once. Also managed to work Ian, GD8BUE and my S2S with GI4KSO/P on GI/MM-007 was particularly pleasing…Seems there’s still some life in the wet noodle :wink:

Big thanks to all the chasers.

73 all
Mike M6MMM


#2

In reply to 2E0YYY:
Hi Mike
Good to work you too - a unique chase for me as well!
Dave


#3

In reply to 2E0YYY:

Hi Mike,

Great to get you S2S on another unique for me, makes a difference to not work you on Shining Tor for a change Hi

shame the WX has changed today for the north west!!??

73

Tony


#4

In reply to 2E0YYY:
Hi mike nice to work you has always it was a pleasure my wife says i talk to you more than i do her hi catch you soon Dave M3XIE


#5

In reply to M0TUB:

In reply to 2E0YYY:
Hi Mike
Good to work you too - a unique chase for me as well!
Dave

Seems you were not alone, Dave.

I remember our qso well, your signal was well down on what I’m used to and it was interspersed with dreadful howling +40 of QRM.

The qrm on Great Orme, can be a real a pain and I certainly wouldn’t fancy doing one of my marathons from up there :wink:

Nice summit though and because of the excellent wx, as busy as Piccadilly Circus. Had to set up about 50m away from the trig point because of the dangers of someone tripping over the antenna guy lines, which I took the trouble to mark with bright yellow plastic. Loads of people came over to have a listen and I spent ages fielding questions. A German ham, DJ1UI who was in Wales on holiday, came over and introduced himself also.

Very interesting activation, however, because of the qrm problems, maybe not one I would go out of my way to do again.

73 Mike
M6MMM


#6

In reply to G1JPV:

In reply to 2E0YYY:

Hi Mike,

Great to get you S2S on another unique for me, makes a difference to
not work you on Shining Tor for a change Hi

Yeah, so many people asked when I would be back up there, LOL.

shame the WX has changed today for the north west!!??

I’m attending two rallies this weekend Tony, so I’m hoping it stays clear…

73 Mike
M6MMM


#7

In reply to M3XIE-1:

In reply to 2E0YYY:
Hi mike nice to work you has always it was a pleasure my wife says i
talk to you more than i do her hi catch you soon Dave M3XIE

Thanks Dave. BTW, I worked Bert, (Egg on Toast) M0EOT/M, he was mobile in Goldenhill. He was really surprised to work me in Llandudno :wink:

73 Mike
M6MMM


#8

In reply to 2E0YYY:
Hi Mike. be interested to know what rig you used. I was up there and used a Yaesu VX150 with a Watson HSMA 270 whip and had no problems. I was up beyond the cafe and on a bit of a knoll.

.d. G4TUP.


#9

In reply to G4TUP:

In reply to 2E0YYY:
Hi Mike. be interested to know what rig you used. I was up there and
used a Yaesu VX150 with a Watson HSMA 270 whip and had no problems. I
was up beyond the cafe and on a bit of a knoll.

Hi Dave, used the FT-857. Yep, I was behind the cafe about 50m away from the trig point. My main concern was for one of the kids (or adults) going base over apex on one of the guys. However, my money would be on the collinear being the culprit. Bit of a shame I did’nt take the dipole as a comparison.

73 Mike
M6MMM


#10

In reply to 2E0YYY:

I was very impressed when I found out that Colin G8JSM/P who successfully activated G/SP-017 Billinge Hill this afternoon, did so using a Wouxon handheld connected to an external vertical antenna (possibly a J-pole or slim jim)mounted on a fishing pole.

Yes, you read that correctly, a handheld with a proper antenna!

But what about the QRM from the commercial transmitters up there I asked?

Colin, a man who obviously knows what he is doing, had made some coaxial stubs for certain frequencies in the 150MHz & 160MHz range, which I assume were broad notch filters. In any case, these did the trick & Colin successfully activated Billinge Hill on 145MHz FM, with a modern handheld connected to an antenna with gain!!!

Maybe it’s just me, but I think that is worthy of some respect :slight_smile:

Well done Colin, if you read this & have any photos or drawings of your stubs, I am sure there will be many here that would appreciate their design.

Thanks & best 73,

Mark G0VOF


#11

In reply to 2E0YYY:
Mike,

For commercial radio sites like Great Orme (including paging and 3 FM radio services) I use a homebrew band-pass filter centered on 145MHz - although it has a little through loss on transmit it’s worth it to hear the stations calling!!

73

Martyn GW4CQZ


#12

In reply to 2E0YYY:
Very interesting Mike. However you are unlikely to work anyone on 2ssb using a vertical antenna as the convention on ssb is to use horizontal polarization and there is a huge loss if you use vertical
John G8XTJ-


#13

In reply to G0VOF:

Impressive indeed. I was surprised when he told me as I had done some tests with normal coax which showed that single stubs did not have sufficient Q to give good differential attenuation.

There appear to be several factors contributing to his success:

The first is that he was not using normal (RG58/RG213) co-ax but a thicker (lower loss?) coax (5/8 inch?) from his junk box.

The second is that he used several stubs (3?)

These things will serve to improve the differential loss.

The final factor is that it is possible that not that much differential attenuation is required. Most people have found that turning the aerial horizontal makes a sufficient difference, suggesting that 20dB might be adequate.

Colin was not able to measure his transmission loss but empirically it can’t have been too bad as he was a good strong signal. He also mentioned that it was a rather bulky solution.

It is worth noting that his set-up is a band-reject filter and so will do nothing to attenuate signals below 2m which may be a problem in some locations.

It would be nice to see some photos and some measurements as they might give some clues to a reproducible design using standard components.

73

Richard
G3CWI


#14

In reply to G3CWI:

There’s a design on LA8AK’s (SK) pages showing a simple notch filter made from LDF 5-50. The design uses a small trimmer capacitor to tune the notch. In his case it was a 288MHz filter for harmonic supression on a 2m transmitter but could easily be used as a notch at ~150MHz.

The downside being it would be around 35cm long. LDF 5-50 is not terribly heavy but the weight of 2 or 3 lengths and some T pieces soon adds up. Interesting to experiment with and odd short lengths can be had for nothing. I wonder if you could achieve acceptable results with miniature hardline like UT-141 instead. However, a lumped circuit maybe more convenient especially for low power operations.

What surprises me more is not that a suitable filter can be made from coax stubs but that the screening of cheap handhelds is good enough that the main cause of the QRM is overloading through the antenna socket and not direct breakthrough of a plastic case.

Andy
MM0FMF


#15

In reply to MM0FMF:

What surprises me more is not that a suitable filter can be made from
coax stubs but that the screening of cheap handhelds is good enough
that the main cause of the QRM is overloading through the antenna
socket and not direct breakthrough of a plastic case.

Do the math. Assume the attenuation of the filter is 20dB. Assume that the screening loss is only 30dB (appallingly bad). The signal hitting the receiver will be 1/100th plus 1/1000th of the external signal. This equals 11/1000th and thus is -19.6dB; a 0.4 db degradation.

73

Richard
G3CWI


#16

I made a helical filter this evening. It’s nicknamed the tenpence filter as it is tuned by two five pence pieces! Measurements as follows:

145.5MHz -5.62dB
153MHz -33.74dB
160MHz -43.08dB

The loss is close to the theoretical figure for the design (4.27dB) although the skirts are not as steep as predicted. However a differential loss of 28dB at 153MHz is probably quite useful!

73

Richard
G3CWI


#17

In reply to G3CWI:
I was surprised at the response that my little experiment generated. I was trying to see if simple stubs could be used to reduce the blocking problem due to pager transmitters. Rather than starting on a mathematical treatise I decided to put something together and try it. The first iteration used thin coax (RG59 I think), I couldn’t see much difference between the response at 145MHz and 153MHz on a stub that was cut for 153MHz.I then repeated the experiment with some larger coax that I had in the junk box. This showed a bit more promise. The coax has a single centre conductor, the shield is a solid copper tape with a copper braid over the top of it and it is about 12mm diameter. The stubs and associated tee pieces and fittings were bulky, heavy and fiddly to set up, Trimming the stubs was messy. I though about using capacitors to tune the stubs, but how do you protect them in the rucksack environment. I used three stubs cut for 153 MHz spaced 1/4 wave apart I had some time yesterday and set about doing some measurements, The 153 MHz signal was attenuated by about 35dB , the only problem was that the 145 MHz signal was about 10dB down, and the vswr on 145MHz was not good. When I was using this contraption the other day it was only in the receive path, with so many PL259 connectors in line I was going to have losses!!! But also I was concerned as to how bending the coax may have affected the frequency response ,vswr etc. I was running the hand-held at 1Watt just in case I inadvertently transmitted through it.

It seems that bigger (or should that be better) coax improves the situation. thinking about it, stubs are tuned circuits, I suspect that I need a higher Q so that the 145MHz signal would not be attenuated . Maybe LDF4-50 or LDF5-50, but this is getting too bulky, too heavy and too expensive. The rig only cost about £120 including adapter so I don’t want to spend more than about £20 to solve this problem

I do not think that this is the right way to go.

What is needed is a high Q and 1/4 wave transmission line, but small size and easy to adjust, robust, and cheap, preferably junk box.

The conversation that I had with you the other day about helical resonators got me rummaging in my junk box again. I wonder if a metal paint can(Hammerite Satin Black ,unfortunately still full, but that’s another job!!) 4 inches diameter 4 1/2 inches long could be used as the outside of a helical resonator, bolt/solder the helix and the rf connector to the lid, drill a hole in the centre of the base and solder a brass nut on , brass screw though base to give tuning cap, from a mechanical point of view the helix will probably need to be self supporting so 4mm or 5mm brass rod probably 4 or 5 turns and about 50mm dia, fed maybe 1/2 turn or less from the earthy end, this should possibly work. I’m looking at chapter 12 page 12.24 of the 2007 ARRL handbook, the nomograph looks a bit daunting, but quite informative. They mention silver soldering and silver plating for optimum results, but… Anyhow for the price of an N type and a bit of brass rod it may be worth a go. Its got to be smaller than the coaxial cable alternative.

Food for thought, I look forward to your comments.

73 Colin


#18

In reply to G8JSM:

Colin

I suspect anyone who has struggled on Billinge Hill will have been interested - it is unusual to hear a station up there on 2m FM that is not struggling!

Here is my take:

This filter is really easy to make as it uses two cheap standard tinplate boxes. The adustment mechanism is simplicity itself and works well. Input return loss is about 15dB.

I could switch it out on transmit to negate the losses on that path.

73

Richard
G3CWI


#19

In reply to G8JSM:

I was just reading about a filter using coax stubs but have lost the link (sadly work got in the way of research so I’ll post it when I find it again) that described the problems you and Richard have seen. His suggestion was to use higher impedance cable for the notching stub at ~150MHz as this reduces insertion loss at 146MHz. He had three sections made from 50Ohm and 93Ohm cable. It consisted of a peaking section for 145MHz using 25Ohm cable and a notch stub for ~150MHz using 93OHm cable, separated with 1/4wave section. He used RG62 for 93Ohm sections and RG58 for the 25Ohm section (paralleled up). IIRC it had about 25db loss at the notch and only 3db at the desired frequency. Using RG58 type cables makes it quite suitable for SOTA as the 3 sections can be coiled up so it’s not big or very heavy.

Now to find the link…

Andy
MM0FMF


#20

In reply to G3CWI:

Never, EVER hit refresh (f5) on your browser after you just posted a comment to the thread or you’ll get a repeat of your last comment.

Andy
MM0FMF