Hi,
I have an old stationmaster vertical for 10m which I have "attempted" to modify for 6m. I followed modification information from an article on the internet. I cut the existing coil down to 4 turns, left the SO-239 tapped cable to the centre of the coil, and reconnected it to the main element tubing. Then I reduced the length of the "main element" to 110 inches as per the instructions, measured from the bottom of the base of the antenna to the tip. Testing indicated 2:0:1 SWR at 52.100MHz. Is there any way of getting the SWR a bit lower? I think that the antenna may be a little short as the SWR decreases as frequency increases. Here is the original modification information. http://www.radioelectronicschool.net/fi ... ster-1.pdf
Any help appreciated
Thanks
Edit: Does the 4 coils have to be physically tied together (i.e. touching) or are they spaced as they normally are in the 10m configuration.
What you are basically trying to do is rescale the antenna from 11/10 metres to 6 metres.
The first question is, have you tried lenthening the main vertical and seeing what that does to the SWR. I am not sure how you achieved your shortening, but on simple method is to not use a screw to secure between aluminium rod sections, but to cut a vertical pair of slots about 25 mm long, on the top of one or more sections. Then using a metal hose clamp, you have the ability to telescope in or out the antenna length.
If you have tried this, then the next thing to try is moving the tap point on the coil. This is looking for a better impedance match.
I have undertaken a conversion on a stationmaster antenna very successfully. My approach was a little differenet in that I worked out what the scale adjustment should be from the original resonant frequency, and used that as my start point.
I removed the old coil and rewound a scaled down version with the same number of turns, spaced slightly wider apart, but a narrower diameter ( about 60%). I used 2mm hard drawn copper wire I had.
I then experimented and lowered my SWR by adjusting the antenna length, moving the tap point on the coil, and even compressing and expanding the coil windings. I comfortably aciheved an SWR of 1.25:1 with a 2:1 SWR range of 700KHZ. I tuned my antenna for 50.200MHz.
Now, one interesting thing. The station master I had inherited had no ground plains. I think this was how they were used on 11 metres. Anyhow, all the google search info kept talking about ground planes on the station master mod. I had two 2.5 metre lengths of 10mm aluminium tube in my shed, so i sat these at right angles on the "C" section that holds the coil. Low and behold, my band width went from 700KHz to around 3 MHz. The antenna was now usable over all inhabited parts of 6 metres.
Hope this is helpful,
In answer to your question re the coils, they should not be touching, but spaced apart.
VK7HAY wrote:Hi,
I have an old stationmaster vertical for 10m which I have "attempted" to modify for 6m. I followed modification information from an article on the internet. I cut the existing coil down to 4 turns, left the SO-239 tapped cable to the centre of the coil, and reconnected it to the main element tubing. Then I reduced the length of the "main element" to 110 inches as per the instructions, measured from the bottom of the base of the antenna to the tip. Testing indicated 2:0:1 SWR at 52.100MHz. Is there any way of getting the SWR a bit lower? I think that the antenna may be a little short as the SWR decreases as frequency increases. Here is the original modification information. http://www.radioelectronicschool.net/fi ... ster-1.pdf
Any help appreciated
Thanks
Edit: Does the 4 coils have to be physically tied together (i.e. touching) or are they spaced as they normally are in the 10m configuration.
Hayden, I interpreted the instructions differently to you... but I think they are unclear.
Perhaps you should email Peter and ask him. If you Google for info on the Ozziepole or Aussipole (a lossier knockoff of the Buddipole) you should find contact details.
All of these types of antennas have an issue with decoupling of the support mast (ie there is no decoupling), and so are sensitive to the height of the mast.
Someone will publish a book on 101 uses for a StationMaster one day!
Hi,
Thanks Owen! I will get in contact. Yes a "Complete Guide to the Stationmaster" would be nice. They are brilliant antennas I'm sure everyone will agree.
Hayden,
I have looked at your link, and I interpret it differently than you, also. I understand they are suggesting leaving the original coil as is, and strapping together (shorting out in effect) the top 4 turns, This effectively reduces the coil by 4 turns, leaving about 6 turns in use.
This mod gives you a 1/2 wave. The mod I undertook was to turn it into a 5/8th wave ground plane, which has the characteristics of a lower angle of radiation. See this link and see if is of benefit. http://www.uksmg.org/vertical.htm
They are not suggesting starting with a Stationmaster, but if you look at the design you will see very obvious similarities.
Good Luck
Hi,
Thanks Michael,
Yes there are definate similarity's to the link you provided & the Stationmaster, perhaps that design was based on a modified one & since they couldn't get them in England he produced a home-brew version. Anyway, I will take all of this into account & do some experimenting on the weekend.
Thank You.
I converted a SM from 11m to 10 by shortening the radiating element and tapping some turns off the top of the coil in a similar way the SO-239 is connected to the coil.. I had my MFJ antenna analyser handy and got it near spot on.. SWR was satisfactory without the tap, but it was little effort to make it better..
I imagine a similar method could be used to get one going on 6, rather than clamping the turns together..
I did a small programming job for a fellow amateur on a FT-8900.. For payment I accepted what was left of an old 11m stationmaster antenna..
So, I set about getting it going on 6m. Firstly I needed to find some aluminium to make the element the correct length.. This was calculated by 150/53x.98. About 2770mm. The first telescoping joint was secured in the usual fashion with a screw and hose clamp. The second section was secured just with the clamp so that the length could be adjusted as needed. I made a 1 wavelength long test cable from RG-58.. I used the MFJ-259B to trim that to the proper length.. I found a short length of mast to get the antenna into the air for testing, and mounted the antenna to the end of it.. I strapped the top 4 turns together as in the VK2EVB article, but the results weren't good, seemed unreliable with the corroded coil tube.. I decided it would be best to use my 10m conversion method and make a tap to tap the top 4 turns off the coil.. I used an old connector thingo and smashed the plastic insulation off it.. To get the connector over the end of the coil tube, I removed the rivet from the coil to element joint, deformed the tube enough to get the connector over the end and reshaped it to fit a self tapper through it and back into the element. In the process of all that I managed to ruin the joint, so I unwound the top turn and made a new joint.. Its only there for support purposes now.
With the aid of the MFJ-259B I went about tuning adjustments, and about half an hour later I had the results I was looking for. 1:1 SWR with 50 ohms R and 2 of reactance at about the frequency I wanted, which is good enough for me.. See attached pictures.
