Category: VHF Radio

RSGB Momobeam – DUO4 4m/6m Dual-Band Antenna

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I have recently been dabbling with 4m at home using my Yaesu FT101MP and a Sirio CX 4-68 vertical antenna, to use the Sirio I have to place it onto my drive-on mast in the garden and feed the coax through the window. I have also played 4m whilst out on some of our Ham Radio Socials with Sri 2E0LKA as the 4M net on a Sunday is one of his favourite nets.

In Aprils version of RadCom (March) there was an article on the RSGB special purchase of the Momobeam 6m/4m dual band antenna, having limited space on my antenna mast I decided to give this low profile antenna a go.
I used to have a longer stub mast on the rotator which held a 3 element yagi for 6m, an MA5B for HF and a colinear for 2m and 70cm but due to heavy broadband adaptor QRM I took the 6m yagi down and reduced the size of the stub mast.
For this installation I did not want to replace the stub mast as that would have been a lot of work at that point if I then decided I didn’t want to leave the Momobean installed. I managed to get a separation distance of around 2.5m between the MA5B and the Momobeam.

A pre-order and a month and a bit later the antenna arrived.

I initially took everything out of the box indoors to ensure that all of the parts were present and correct. To obtain the installation instructions I had to scan the supplied QR code, I then printed them off ready for the build. Each antenna part was clearly labelled as were each of the bags containing all of the required fixings and tools required to build the antenna.
I decided to build the antenna by attaching the boom to my drive-on mast in the back garden as having the antenna elevated aided in its construction and checking the VSWR after the build.


As with any build it pays to read the manual first before starting, failing to do so could quite easily lead to build problems. An example of this is the element clamps, some of these have been modified to seat the element on top of the clamp. Another example of this was the way that the smaller part of element was fixed to the larger outer part of the element, here a larger diameter hole was made on one side of the outer element allowing the hex bolt to sit directly on the inner element. When the nut was fitted and tightened to the other side of the outer element which created a very strong joining of the two elements with absolutely no play.

Once I had finished building the antenna I attached some coax and a RigExpert AA-230 Zoom to check the VSWR on both 4m and 6m. The profile looked as you would expect with a VSWR between 1.3:1 and 1.6:1 for 6m and between 1.3:1 and 2.0:1 for 4m. The profile changed once up on the mast most lightly due to interaction with other antennas and metal up on the mast with 4m still sitting between 1.3:1 and 2.0:1 and 6m sitting between 1.8:1 and 2.0:1.

The ATU on FT101MP does not work for 4m so this was were the antenna needed to have a good tune to make it usable. For 6m the ATU works and therefore the slightly higher VSWR wasn’t a problem.

The next job was to feed some coax into the attic and down into the shack. There is still QRM from internet adaptors on 6m and some evidence of this also on 4m. So far, only a couple of days and there hasn’t been any Sporadic E to talk about to enable the testing of the antenna in anger. There are some local 4m nets but most of the stations that participate are vertically polarised which equates to a lot lower signal strength to the norm on the Siro vertical.

Overall the antenna construction was pretty simple and the build quality of the antenna and parts very high. For the cost of the antenna and its low footprint its a good buy. I will report back on its performance as and when time and conditions allow.

Ham Radio Social – Old Winchester Hill

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Another Ham Radio Social this time the QTH was Old Winchester Hill Carpark but this wasn’t the original intended location for this portable operation. The intention was to setup at our usual haunt “Teaglease Down” but upon arrival we were greeted with a strong cold northerly wind so the decision was made to move further along the ridge to Old Winchester Hill Carpark. We normally stay away from this location as it can get very crowded on a Sunday but for this session it did afford some good shelter from the wind.

2E0LKA Sri had purchased two new antennas to try out on the Sunday morning 4 Metre Net, these were a Sirio CX 4-68 4m and a Sirio SY68-3 3 Element Yagi. We tuned the vertical with a RigExpert AA-230 Zoom achieving a VSWR of 1.2 across the band which was then connected to a Motorola GM350 25W 4 Metre radio. Sri had pre-tuned the Yagi prior to coming out and Steve 2E0OWI connected this to his Anytone 4 Metre Handie.

Sri and Steve participated in the net whilst I played around with different tech and various ways of taking photos and video. The idea of the Ham Radio Socials are to get out, play radio, experiment and chat with like minded people (good company) with the obligatory breakfast tsunami of Sausages and Bacon.
If you fancy joining us drop me a message on the contact page.

Radio Social Combe Gibbet

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So another Sunday Ham Radio social, the QTH this time was Coombe Gibbet located on Gallows Down sitting on the border of Hampshire and Berkshire. In attendance were Myself, Steve 2E0OWI, James 2E0HHP, Sri 2E0LKA and Tiago not yet licenced but watch this space.

Today the guys were QRV on 4m, 2m and HF with a good selection of antennas for experimentation. There was even a little smattering of LoRa Meshtastic in the guise of a LILYGO T-ECHO placed on the back of the truck. Although the sun was out it was still pretty chilly on top of the hill . The clear sky enabled good views of the 3 counties consisting of Hampshire, Berkshire and Wiltshire. We of course had the obligatory bacon and sausage wraps and plenty of coffee to keep us going.

There was plenty of wildlife spotted for the day including Hares, Red Kites, kestrels and skylarks who’s song you could constantly hear on the breeze. Either side of the ridge consisted of the Inkpen and Walbury Hills SSSI with the wildlife clearly thriving here. Across the top of the ridge is a byway which in places was quite rough but as were were all in 4×4 capable vehicles this added a bit more fun to the day. During these /P outings where there are members of the public around we generally always get someone asking us what we are doing which then gives us the chance to be an ambassador to and promote this great hobby and today was no exception

A friend joined us today, Tiago who moved to the UK from Brazil. He is very interested in getting his Ham Radio Licence as he has friends back in Brazil who are licenced operators. During this session we took the opportunity to introduce him to HF where he had a chat with a station on 40m and later on with a station in Kentucky on 17m.

All in all another pleasant Sunday Ham Radio Social.