Category Archives: Antennas

So much, where to start…

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Well hello, maybe your reading my blog on amateur radio – I had a very nice weekend off and relaxing/downtime getting things done, but with that there was ALOT be done with regard to Amateur Radio !

Where do I start… well, lets first say thanks to my good friend and fellow radio amateur Trevor (PA2TG) who has been absolutely amazing in offering me advice on what I’m about to talk about ! So here we go !

40ft Moonraker mast with 2 Meter JPole

So I have got (two) new masts, willl talk about the other in another posting one day, but lets focus on the the fibreglass 40ft one for now.

Despite Covid, nature is still making some lovely flowers… time to go home after walking the dog, finish work and make a cable

I took some careful time rigging, i used the lightweight rigging but I really didnt want to start with. This looked good, and I got the mast upto full height. The problem then become apparant that my coax was now too short ! At 30m in length, at the time that seemed long enough as i was using my buddipole then and the coax was purely for experimental purposes.

Stripped of the sheath

The 40ft mast, is amazing, i will give it its own posting, in this post I want to concentrate on the coax I made for the mast as I’ve got some great advice, with more understanding about coax and loss that I could of ever asked for thanks to Trevor. I will point out that I ordered and received the coax a while ago, before speaking to Trevor, but I now know what to order next time, and it will make me appreciate what I have and how much power is being lost in the coax itself (you would think not much, but suprsingly, even the top quality coax, has some loss!)

watching the core slowly emerge.. the thread on this plug is very fine

So the Coax I had is https://www.radioworld.co.uk/rg-8-mini-coax-cable-50-ohm-military-spec-50-metre-drum – I really dont undertand all the specifications, and the price is right. I soon learned from Trevor not everything is what it seems and also websites on coax/loss confirmed what he had told me http://m0taz.co.uk/2017/11/coax-cables-and-associated-losses/ This cable is RG8, so of my 10 Watts going up the cable, on 2m 3.5w will reach the base of the antenna, so getting 1:1 S.W.R. is really important ! (3.5w !!?!LOL!>!!!)

first some electical tape, then heatshrink, looking rather good if I dont say so myself !

So I set about making my cable with the coax, I found this video most useful https://www.youtube.com/watch?v=GjO5ERU6a78 and following it found that I had created an awsome cable. Now if I was honest, that would be the end of it, but I have to admit I made rather hilarious mistake… In the video he does a continuity test, to ensure the cable is shielded and the center pin will deliver the RF power/energy.. I thought, well, why not strip the other end and check from both ends ! Great idea M7ALU ! So I stripped the other end.. measured continuity, come on 0… 1… a solid 1, not any reduction.. traces cable.. i’ve stripped the cable from the reel… So, when stripping cable, make sure you get the right one.

Putting a SO239 on to make sure it will fit on the mast / jpole connector ok

In the end I stripped. sheathed and plugged my cable in with loads of testing for continiuity, because I dont want to get it 40ft+ up and find its not working. Results soon.

a completed cable, both ends done, 0.0 on the power meter measuring continuity

Tomorrow she goes up, lets hope 1) I got the length right 2) it keeps working 3) The cable is good enough spec for me on 2m/70cm and 10 Watts of power.. We shall see !

40m with the Buddipole Extended Whip Arms

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I set about setting up my Buddipole in a 40M (7Mhz) configuration. For this i added 2 new extended whip arms to my collection of Buddipole parts. The majority of my Buddipole parts come from Radioworld, who I really dont mind promoting in my blog as they are very quick on delivery.

To start with I used the “Buddipole in the field’ setup recommendations, which helped get the physical setup. Of what to plug in where, as I’m still learning it really helps having a printed A4 page with the diagrams on, and I stuff that in my pocket or my external table as I work along.

It took me about 15~20 minutes to get the pole and the whips setup at ground level. The whips are really long at 9ft which is what you’ll need for 40M and they must be fully extended. Take your time pulling them out from the tips and firmly, but gently extending them.

aobe roof level and secure

Now I dont mind saying I have already lost two smaller (5ft) whips with messing up guying and the Buddipole nearly falling on me, so if you are reading this, please, please take your time with guying/rigging your buddipole up. Mine moves around my backgarden, so i dont have a static mount point, I could use Pythagorus equations to work out the technical lenght, but I find that rasing the antenna, checking the tensions and taking it back down and then up as required is the safest. When I’m indoors and it starts getting windy, i want to know that its not going to fall !

Anyhow after guying and getting to an ok height (above the roof line) I started on tuning the S.W.R. inital results were a little disappointing, as I expected some loss on rising, but it got a bit high. So I brought the dipole down again and spent more time on the coils.

hmm, not bad, but not what i was after

Getting the coils setup was a real exercise in patience – having not done this for a specific frequency before, it took a few good attempts of going from left to right coil to get the nice curve I got below.

The S.W.R. on the lower frequencies is a bit high, but as I’m not going to be attempting morse (yet), thats not a concern to me.

Improved SWR on 40m

I was quick to take some photos of the coils to log where I had put them, maybe next time i can get a better improvement, but this is where I had them this time.

Black coil – almost right to the very end (versatee to the right, whip to the left in this pic)
Whip to the left, versatee to the right in this pic.

I got in and even tho it was getting later and the sun going down had a great time tuning in and listening on 40m. It was very busy on the voice frequencys and finding a gap to transmit and knowing I was ‘spilling’ over to others was a bit nerve racking.

I did try putting a CQ out, but no response, but the SWR reading on the radio was very good, even tho i am only using 10W.

So next time I will show more about the CAT and digital interface I now have, but thats another post 🙂

All the best and 73’s from M7ALU

Wet and Windy – but some action on 40m!

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tuned into 40M

So the bad weather continues in the UK, i had wanted to carry on with my 2m/70cm antenna project but with the gales, it didnt seem like a sensible thing to be doing, esp as the mast is tall and heavy – even with a light breeze, it could be dangerous.

Instead I looked thru the Buddipole in the field document and reviewed the 40M section. It said it was possible, albeit with a slightly higher SWR.

its 40m but at about 2m in height…

So with the bad weather I got the buddipole setup, not wanting to lose any more antenna, I kept the height at about 2m verticle and guyed down the mast as usual and also thru the veresatee to give some extra support on the horizontal element of the dipoloe. This worked really well as the winds did pick up and mast held up well in the eright location.

I was only able to get my SWR down to 5, probably due to the height of the antenna, but amazingly I was able to receive ! Given I’ve not had alot of action on the Kenwood I was so happy to tune in and listen in. Some points I could get both ends of the conversation, others just the transmitter, but nevertheless, i found it a worth while excersie in setting up the antenna in inclement conditions and also being to use the Kenwood on HF.

Do some more investigation, one other configuration I could try is a ‘NVIS’ on 40m. This is well documented here and as I’m short one wire and the clearance mounts will probably do it another day (having just got over a bad cold, dont want to risk getting ill again !)

So for now here is a video of one of the many stations I could pick up on 40m. It was great, and amazing to see how the sun going down quickly effected the transmisions ! (80m is popular after sun).

2m/70cm antenna – on a flag pole

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To free up the buddipole for HF, I wanted a 2M antenna for the ICOM 2200-H I could use with ease. I investigated making a copper J-Pole, or Super J-Pole to be more precise, to increase the gain and range. Having worked out the costs, which after equipment, tools and consumables came to almost £100 !

With that I took to the internet to search for an alternative and found the MOONRAKER WTZ-270 J POLE ANTENNA for £37.98p (including shipping & VAT). So I already have the coax/connectors and a flag pole for hoisting it up on.

First job was to check the S.W.R. (I punctuate S.W.R where I can after I got caught saying SWR rather the short for acroynm – I’m not on 27Mhz here ;). I connected up my analyzer, and sure enough right in the 2M and 70cm a stunning reading of 1.3 SNR.

The flag pole has a decent plastic top, so I bolted the antenna to that, giving it isolation from the aliminum pole.

Now I quite forget how tall this flag pole was, but its a heck lot talller than my buddipole is, so I made sure that the weights were securing it. For the moment this was ok as I was supervising and it wasnt windy. I gave the mast a really good tug and with my weight it wasnt falling over anytime soon. The antennas weight with the bracket was very light, so no concerns there.

With that I headed in to my trusty Icom and started going around the local repeaters. I was not disappointed ! Immediatly stronger signals and clearer reception. A tried all the local repeaters and gateways, no problems there… So i thought, time to really test how far I could get on 10W, and tapped in the Southampton Repeater… amazingly it worked ! I got someone on /M and we could both make each other out, whilst not 5/9’s it was good enough and the furthest I had ever got on 2M and 10W – I think height and the antenna really done well.

So forecast for the weather in the UK this weekend is for high gales, and whilst I the mast & antenna are a good distance away from the public and buildings, i thought why risk it, and have taken it completely down tonight.

Good news is that will mean pictures for the next post, and maybe even a video – especially if I can reach Southampton again on 10W which is a good 30+ miles away and with some big hills between us.