50, 70 and 144 MHz in one beam.

I have always enjoyed taking part in the UKAC series of contests, they are very busy and ideal for portable operating in the summer months.

Not so much fun in the winter, but the chance to operate from home required a beam. I have tried to take part with a vertical co-linear, but the crossed polarised loss and my limited takeoff resulted in very poor results. The RSGB has recently added an FM section to activity evening, but while this is interesting to achieve any distance SSB is the mode.

Here is a typical portable setup, this one was in December!

I operate the Icom 7100, and this can facilitate 50, 70 and 144 MHz in SSB, so was looking for a beam that could do all 3 bands. DK7ZB has a design on his website that covers all 3 bands, with a very short boom. Yes, it’s a compromise antenna, but working on the principle it’s better than nothing!

 

The boom is just 1.2m long, and it is a single 50 Ohm feed.

The design is detailed on Martin website, the antenna is a 2e on 50 and 70 MHz and 3e on 144 MHz

I found the antenna very helpful at my QTH, allowing a small discreet 3 band yagi to be installed and me to take part in the UKAC contests. Here you can see the antenna around 7m high.

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Coax Cables and Associated Losses

As a newly licensed amateur, one of the points I found hard to grasp was feeder losses. While it was explained to me that feeder cable had losses, it was sometimes hard to visualise what this meant in the real world.

The maths can be a little scary, and so in this article, I have looked at some real-world examples.

So we all appreciate that coax has losses, and we understand these increase with frequency and have a direct relationship to the length of the coax. Coax of course also has a maximum power handling rating, although this isn’t applicable to foundation licence candidates it’s worth considering this as you work towards a full licence and the ability to run 400w.

The amount of RF power (and received signal) will always be less than we put in, it’s worth taking a moment to consider that this applies to both transmit and receive signals as losses work both ways. The addition of a Low Noise Amplifier at the masthead will help to offset the receive losses, but it will do little for your transmit power. Often we say that’s fine, I will just use more transmit power, but that’s not always possible unless you have linear amplifiers to hand.

At HF (below 30 MHz) the losses are not significant, and we can usually opt for RG58 or RG213 coax, but as we move up the spectrum 144 and 430 MHz present a different challenge. The quality of your coax now becomes a significant factor in how your stations perform, and investing in good quality coax will often provide a better return than spending more on your antenna.

Let’s assume we have a typical coax run of 30m (100ft in old money) and we wanted to review the actual power presented to the antenna for various coax choices.

In this example, we have a radio with 10w (Foundation Licence) out and will be using 30m of coax. So for each frequency, we can now read off how much power will actually reach the base of the antenna.

Power 10w 30 MHz 50 MHz 146 MHz 440 MHz
RG-58A/U 5.6w 3.9w 2.46w 0.9w
RG8(mini8) 6.3w 6.16w 3.54w 1.54w
RG-213 8.7w 7.4w 5.24w 3.1w
LMR-400 8.5w 8.12w 7.08w 5.36w

The same figures have been calculated with 50w (Intermediate Licence)

Power 50w 30 MHz 50 MHz 146 MHz 440 MHz
RG-58A/U 28w 19.5w 12.3w 4.5w
RG8(mini8) 31.5w 30.8w 17.7w 7.7w
RG-213 43.5w 37w 26.2w 15.5w
LMR-400 42.5w 40.6w 35.4w 26.8w

So for every pound invested in your coax, performance will be increased on both your transmit and receive path. The actual coax you choose may well be influenced by the route and the bend radius, large diameter coax doesn’t bend very well.

Just to complete the picture, the last example is using 400w (Full Licence)

Power 400w 30 MHz 50 MHz 146 MHz 440 MHz
RG-58A/U 224w 156w 98.4w 36w
RG8(mini8) 252w 246.4w 141.6w 61.6w
RG-213 348w 296w 209.6w 124w
LMR-400 340w 324.8w 283.2w 214.4w

The figures have been calculated by looking at the feeder loss in dB/100m. These figures are a guide and provide the typical power (loss) seen for these coax types. The actual figure may vary, I have not considered coax connectors and adaptors as the quality and losses vary, so your measured RF power is likely to be even lower as the losses increase.

In selecting your coax you may want to consider the dB loss figures quoted by the manufacturer, the lower the dB the better in this example.

loss/100m (dB) 30 MHz 50 MHz 146 MHz 440 MHz
RG-174 16.5 19.8 39 75
LMR-100A 11.7 15.3 26.4 46.8
RG-58A/U 7.5 12.3 18.3 31.2
LMR-200® 5.4 6.9 11.7 20.7
RG-59 x 7.2 x 22.8
RG-8X 6 6.3 13.5 24.3
LMR-240 3.9 5.1 9 15.6
LMR-240 Ultra 3.9 5.1 9 15.6
RG-8/U FOAM x 3.6 x x
RG-213 1.8 4.5 8.4 15.3
RG-214 3.6 4.8 8.4 15.3
LMR-400 2.1 2.7 4.5 8.1
LMR-400 Ultra 2.1 2.7 4.5 8.1
DRF-400 2.1 2.7 4.5 x
Bury-FLEX x 3.3 x x
9086 x x x 8.4
9913 2.4 x 4.5 8.4

And lastly maximum power rating for typical coax types.

Max Power Handling 30 MHz 50 MHz 150 MHz 450 MHz
LMR-100A 230 180 100 60
RG-58U 400 300 160 80
LMR-200 1020 790 450 260
RG-59 500 400 250  x
RG-8X 350 280 150 80
LMR-240 1490 1150 660 380
RG-213 1800 1200 620 300
RG-214 1800 1200 620 300
LMR-400 2100 1700 1000 550
DRF-400 3300 2570 1470 830
9913 2200 1700 900 450

 

The following online resources will help you calculate losses.

dB calculator

Coax attenuation chart

Coax type v loss

 

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CQWW SSB 2017

The CQWW SSB event runs over the last weekend of October and covers all contest bands from 1.8 MHz to 28 MHz. The event is one of the largest international events of the HF calendar and encourages stations to operate from far-flung and exotic parts of the world.

We opted for the sun-drenched shores near Ongar in Essex, using our contest site at the Kelvedon Hatch Secret Nuclear Bunker. We had decided before the event it would be more of a casual entry, as the contest had started at 00:00 Hrs on the previous Friday/Saturday morning. We have previously taken part in the event, with a most notable event in 2015.

This year we used a 7 MHz vertical, with elevated radials, and a 3e multiband beam for 28/21/14 MHz @ 10m.

3e Multiband Beam

7 MHz Vertical

The HF bands remained in good shape, with some good openings on 28 and 21 MHz and the vertical worked well at 7 MHz. The lower HF bands were predictably crowded, so I concentrated on search and pounce on the higher bands.

George M1GEO and Fred G3SVK with a great sunset behind.

QSO and DXCC per band.

28 MHz provided some interesting DX with a lot of station from Argentina, Brazil, French Guiana, Chile, Suriname, Namibia, South Africa, Qatar and Reunion Island.

28 MHz QSO Map

All Bands QSO Map

In total, we worked 417 QSO in 76 DXCC and had some fun on the bands.

 

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National Hamfest 2017

The National Hamfest 2017 (29th and 30th September) was once again held at Newark Showground. The site provides a large area for both camping and caravanning, with the show opening on Friday and continuing on Saturday.

The location provides the ideal opportunity to meet up with friends from around the country, and browse the stalls both inside and outside.

All of the major dealers had a presence, although the Waters and Stanton had downsized to little more than a boot sale table.

Icom had the new IC7610 at the show, and you could twiddle the knobs but no clue on the RRP right now. Most of the dealers have a suggested price, but Icom says this hasn’t been confirmed.

Food was available from both inside and outside vendors, and the weather was good enough to sit outside once again this year.

Attendance seemed a little down from previous years, but this often happens with this type of rally. I spotted the crews from ICQ podcast and TX Factor both making content and you can watch/listen to this on their websites.

The CambHams team and Flossie operated on HF and VHF from the event.

Dave G7UVW reviewing one of his previously owned (junk) surplus equipment purchase.

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CQ WW RTTY DX Contest

The CQ WW RTTY contest runs towards the end of September, and this year George M1GEO and myself decided to enter the contest under our own callsigns from our contest site at the Secret Nuclear Bunker.

We decided to keep it simple, using just two aerials.

1/ 80m dipole @ 30m

2/ 40m 1/4 wave ground mounted.

The 40m vertical is a tried and tested antenna, but on this occasion, we decided to try elevated the radials.  Peter G0DZB highlighted an article from N6LF, suggesting that elevated radials increased the performance of your vertical. I decided to purchase some plastic posts to elevate the radials 1m above the ground. The plastic posts are designed for holding up electric fence wires and so ideal for the job. The radial system required at least 4 posts, and the results were noticed almost immediately.

 

The VSWR was much flatter across the entire 40m band, and so the antenna was connected to a 1:1 balun and fed with coax.

Both George and I used the solid-state amplifiers by Expert, the 1.3KFA ideal for running 400w RTTY.

 

The M1GEO station with tea, Cola and some Reggi Reggi sauce, all field day essentials at hand.

The M0TAZ station

 

Over the course of the weekend, with some casual style operating I had worked 390Q in 42 DXCC. The highlights for me was working Panama, Indonesia, Thailand, Paraguay and Argentina.

 

21 MHz was open, although I decided not to take my 4E beam and opted to press the 7 MHz vertical into service on this band. It worked quite well, again no ATU required.

 

 

A field day is never complete without some excellent food from Fred G3SVK and Dianne. On Saturday they provided a lovely curry and on Sunday a spaghetti bolognese. Very much appreciated by everyone.

Camping over for the night gave me a chance to appreciate the sunrise on Sunday morning.

Altogether a very enjoyable weekend, in some great September weather.

 

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SSB National Field Weekend with Camb-Hams

This year I joined the Camb-Hams for the SSB National Feild Weekend from their contest site in Worts’ Causeway, Cambridge. I arrived on Friday afternoon to assist with the setup, this included antenna for both 144 MHz and HF for the field day. The HF event runs in parallel with the VHF event over 24 hrs, so Flossie provided a comfortable and warm shack for the entire event.

The VHF event used 2 x 17 element beams at 12 meters, plus 1 further 17 elements on the top of Flossie at 20m. 400w was delivered from a Gavin M1BXF solid state amplifier.

HF used a 3 element tri-band antenna covering 10/15 and 20 meters. Dipoles were added for 40 and 80m from the SCAM mast. 400w* was provided by a solid state amplifier, and mains was provided by 3 x 2kW Honda generators.

The event was very well attended, with Dave GW4ZAR getting the award for furthest travelled, having driven down from North Wales. Others had travelled from Suffolk, Norfolk, Essex, Berkshire and Cambridgeshire. In a first for a field day, the Cambridge 105 tech crew did their waffle live on air from the field day tent. Thankfully the weather held fair, as the noise from the rain on the tent would have been interesting.

Martin M0YRM (Left) and George M1GEO

The contest started on Saturday afternoon and for the next 24 hrs, the radios were pressed into action, making contacts all over the world. I don’t recall any big DX, as it’s a region 1 field day the largest constituent in the HF log would be Germany.

I completed a couple of stints on HF, working mostly EU with the off USA on 20 meters.

Breakfast, Lunch and dinner were provided by the Camb-Hams facilities team, Rob M0VFC and Laurence M0LCM both preparing some great burgers, sausages and bacon when ever anyone looked hungry.

James 2E0JFM and Laurence M0LCM

Altogether a really enjoyable weekend, providing time for both the social side and some contest operating. Further pictures from the event are available here. Thanks to the team at Camb-Hams who made it happen.

*Due to a rule change the SSB FD now carries a maximum power of 100w. G3PYE will therefore only submit a check log for this contest.

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© 2015 Dave, M0TAZ