1/4 Wave Antenna Calculator

I have been making a few 1/4 wave antennas lately, mainly for UHF and the GHz bands with good success, so I decided to create a calculator to simplify the process and maybe get some people who have not tried one before to give it a go.

For UHF for example, these can be made very cheaply, very easily and they perform well. Try one on 433MHz plugged into your handheld for example 🙂

Go to the 1/4 wave ground plane calculator

The 1/4 wave ground plane

The calculator is at m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/

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A long break…

It’s been a year to the day since I last posted an entry here. I have had quite an inactive year with regards to the hobby. Work takes priority of course, but I will get out and about this year and posting a bit more on my blog / pages. I do have some things to update and new pages to add when I have the time such as constructing a 20 element 1.3GHz Yagi, building a 1.3GHz system & some PSU reviews. l also have a few messages and comments to reply to which I am getting through slowly.

It’s been a long winter but spring is finally here so it’s time to get back into the swing of things 🙂

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My first 23cm 1297MHz contact!

I recently purchased a 23cm transverter from SG-lab. It’s a 145MHz IF with a L.O. frequency of 1152MHz (default; can be changed). Output power is 2w. Tonight, I had my first QSO on the 23cm band with it with two friends who both have the same transverter, G7UVW and M1GEO. I used a Yaesu VX-6 for the IF, but that went flat, so I switched to the Icom ID-51, which is set to record all QSO’s, so there is an MP3 below!

The transverter comes with a HB9CV antenna etched on a PCB which works really well. I had the ID-51 in one hand and the antenna in the other, holding it out the window. All three of us had the same setup holding the antenna out of or near a window. I first spoke to David G7UVW at 2.2 miles and then George M1GEO at 1.2 miles. Signals were good all round, although it seems the best signal between G7UVW and I was via reflecting off a school building opposite me (or something, the peak signal certainly wasn’t in his direction!).

We are all very happy with the result. I am now going to build a couple of Yagi antennas, look at getting a PA and try out some of the 1.3GHz UK Activity Contests in the summer.

23cm Transverter

My first couple of 23cm QSO’s using a 2w transverter and a handheld.

George M1GEO setup with the HB9CV on a broom stick boom!

The setup of George M1GEO with the HB9CV on a broom stick boom!

Update: The next day, George M1GEO took his transverter up to the 12th floor at UCL in central London. We made contact easily again both with 2w and a HB9CV antenna, over a distance of 14km.

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Icom IC-7100 SO-239 to N-Type

Icom don’t seem to like N-Type connectors. I have an X-50N Co-linear, with about 5 metres of Westflex 103 of which both ends are terminated with an N-Type plug. I used to have the Yaesu FT-897D, which is why I have the N-Type attached for VHF and UHF. Yaesu (at least in Europe) use N-Type chassis sockets for their UHF transceivers, but Icom use the SO-239, unless you buy something like the IC-9100. Since buying the IC-7100, I have been using an adapter.

Today, I decided to change the chassis socket on the Icom to an N-Type. Conveniently, there is no soldering involved. They have used a sprung clip to connect to the socket pin. Perhaps this helps prevent connection problems due to thermal expansion and contraction between the chassis and PCB or any movement in the connector pin itself. You could probably change it without opening the case, but its nice to see what you are doing and to know you are not bending the clip! Below shows the internal socket connections.

Icom IC-7100 RF Connectors

Icom IC-7100 RF Connectors

Icom IC-7100 N-Type fitted for VHF / UHF

Icom IC-7100 N-Type fitted for VHF / UHF

Before changing the socket, SWR was around 1.5:1 at 433MHz with the original SO-239 and PL-259 to N-Type adapter. After changing the socket to a plain N-Type and removing the adapter, SWR is 1.1:1 or better from 430-440MHz (Shown by the transceiver). It shows how critical things like connectors and adapters get at UHF, although most of the miss-match was probably the adapter. It also makes it easy to remember which port is HF and which is VHF/UHF. A mod well done. If only Icom built them with N-Type sockets in the first place! Oh, and whilst I had the lid off, here is a photo of the inside of the IC-7100 🙂

1:1 SWR after changing the chassis SO-239 to an N-Type socket

1:1 SWR after changing the chassis SO-239 to an N-Type socket

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RSGB 21/28MHz Contest

RSGB 21/28MHz Contest - 4th October 2015. Operating from Kelvedon Hatch Secret Nuclear Bunker.

The 15m and 10m beams.

A few of us decided to have a go in the RSGB 21/28MHz contest on Sunday. We used Georges call, M1GEO and a combination of equipment from us all. I brought my 3 element 28MHz Yagi, Dave M0TAZ brought the two masts and his 21MHz 4 element Yagi, while George and his dad brought the Icom IC-7700 and generator. Fred G3SVK also came and done some CW.

UK stations can only work outside the UK and non UK stations can only work UK stations. This made it quite hard work as there was not much activity due to the bands not being in good shape, especially 10m. We could hear some beacons though, although not strong, we received a beacon in Brazil and one in Argentina. We did work some good DX however, including South Africa, Uruguay, Brazil and VP8NO in the Falkland Islands on 28MHz.

The operating table.

The operating table.

Still, we had fun operating outside in the October sunshine for possibly the last time this year!

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Practical Wireless 70MHz Contest

70MHz DK7ZB 12.5r Yagi on Racal PU12 mast.We had a fun day up at Kelvedon Hatch on Sunday for the Practical Wireless 70MHz contest with fantastic weather yet again!

Dave M0TAZ was operating with his Racal PU12 mast and IC-7100 and I brought along my amplifier and Yagi for this once a year event. There was good activity although as predicted, the final hour was a bit slow going.

We were operating for the whole four hours, running 160W into an 8.24dB Yagi giving an ERP of ~1kW and we worked a total of 47 stations, of which the best DX was GM4JR at 454km. We also worked into Wales and The Netherlands.

As PW contests do not give you a QSO map, I plotted my own in Google Maps by exporting a KML file from the Minos logging software. The QSO map can be seen here.

A photo of the field can be seen below…

PW 70MHz Contest 2015 at Kelvedon Hatch

PW 70MHz Contest 2015 at Kelvedon Hatch

I also took some video on my phone, which can be seen below…

You can also read Dave’s article on his website. George M1GEO, Chris G8OCV, Dave M0YOL and some others also attended to play some radio so it was a good day all round!

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RSGB 2nd 70MHz Contest

2015_70MHz2_1

M0UKD/P – 70MHz

We had some great September weather today for the 2nd 70MHz contest. We setup at the Kelvedon Hatch ‘Secret Nuclear Bunker’ as seen above, using my new 70MHz amplifier at 160w and my 4 element DK7ZB 12.5Ω Yagi.

QSO Map

QSO Map

Conditions seemed quite normal, we worked no Scotland or Ireland but our best DX (as many others) was PA4VHF at 449km. Other highlights were GJ3YHU in Jersey and M1CJN/P in the North York Moors. Total contacts was 46.

A very enjoyable day of operating and testing the new amplifier. Next week, it’s the Practical Wireless 70MHz contest, so lets hope for the same weather and some band openings perhaps? Maybe I’m asking too much 🙂

The Claimed Scores are available. Thanks to Dave M0TAZ, George M1GEO, Dave M0YOL and Chris G8OCV for help & company, and of course everyone we worked (or tried to work!).

RSGB 2nd 70MHz Contest at Kelvedon Hatch

RSGB 2nd 70MHz Contest at Kelvedon Hatch

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