Runboard.com
Слава Україні!
Community logo


runboard.com       Sign up (learn about it) | Sign in (lost password?)

 
Ivy Watts Profile
Live feed
Blog
Friends
Miscellaneous info

Freebander

Registered: 05-2011
Location: S. Cheshire
Posts: 70
Karma: 0 (+0/-0)
Reply | Quote
posticon A Wideband Vertical to cover 24.5 to 29.5 Mhz !!


.

As I have reported elsewhere, I have just purchased a new Yeticom Optima. My choice was purely based on an excellent 'write up' and video of it on the Transmission 1 Website, plus the Manufacturers specifications (and we trust those, don't we !!).

For those who are not Au Fait with the Optima, it covers continuously 24.500 to 30.000 Mhz, and the problem to me was to design a single vertical antenna to be resonant at any frequency the Optima covered. You see - it covers the Amateur 12 Metre Band at 24.500 .... and the 10 Metre Band at 28.000 to 30.000 Mhz. Plus the 'shady bits' in between.

I have had a flash of inspiration, which was painful - and having already made a 'steerable' satellite dish using a 12 Volt car windscreen motor .... why not physically alter the length of (say) an initial prototype 'Cheapo' 5/8 Silver rod, by having a 'Trombone Joint' that could be moved over about 6 to 7 inches, by a 12 Volt (50 pence from the local car breakers) windscreen wiper motor ??.

I am not an engineer, and have no workshop these days, or even any tools - other than a soldering iron, a few screwdrivers, a multimeter and a friggin' big hammer. So is there anyone who has the expertise and knowledge in our select FB Group who would like to take up the challenge to produce a prototype - or better still 2 Prototypes (one for me!) at my expense for parts (The antennas will cost about 25 pounds each!, plus motors, waterproof casing, etc.).

As a matter of interest - possibly not a lot of movement is required, as my current 5/8 Silver Rod, has a SWR of under 3:1 over a bandwidth of 3.5 Mhz (25.5 - 29.0 Mhz), peaking at 27.5 Mhz at 1:1.5 ..... So I would guess with a requirement to extend that range by 1 Mhz at the top and bottom of this Range, the movement of the trombone to bring (say) 4:1 down to at least 2:1 over the whole 24.5 to 30 Mhz may only be about 3- 4 inches of movement in the 'Trombone Joint'. I have made rough sketches as to how to work this, which I would be happy to discuss with a competent 'constructor' over the telephone, or even personally if they are anywhere near my QTH (The Monkey Park at Trentham Gardens, near Stone, Staffs).

Anyone 'Up for it' - better still to build it, get it patented and market it. Its not too late for me at 76 years of age to have ambitions of being a millionaire !!
(But you will have to hurry, as I want to enjoy the fruits of my idea before I curl up my toes !!).

This is the old fashioned idea of doing things - the way it used to be in Amateur Radio - experimentation, and sharing. Free to all !!!

73's de 26FB89 (and other callsigns)

Terrence the Terrible

.

 



---
26 FB 89
Kenwood TS520SE HF Tx
Yeticom Optima 10/11/12 Mtrs Tx
ICOM PCR1000 - 100 Khz to 1300 Mhz Rx
5/8 Wave 'Venom' Silver Rod
Wire dipoles 40/20/15 Mtrs
M0AQC Digital Modes Interface

20/Jul/2011, 3:34 pm Link to this post Send Email to Ivy Watts   Send PM to Ivy Watts Blog
 
madmark1 Profile
Live feed
Blog
Friends
Miscellaneous info

Accomplished DX-er

Registered: 10-2009
Location: Abertillery
Posts: 454
Karma: 9 (+9/-0)
Reply | Quote
Re: A Wideband Vertical to cover 24.5 to 29.5 Mhz !!


Hi Terrance, its not a bad idea, there are antennas that already use a simular idea, the ATAS antennas from yeasu use a small motor to pysically shorten the antenna, Theres also the steppir yagi antennas.

It maybe easier to just extend the actual matching coil thats located in the antenna base by adding a few extra turns to it to allow it to be resonant on 24 mhz, These extra turns could be shorted out by a small relay to allow the antenna to be resonant on 28 mhz and in between.

Its one idea, obviously a relay brings its own problems such as it needs to be powered, same goes for the motor option you suggested, you could also have used a 'trap' but as the seperation between the frequencies isnt really enough then it may not work so well.... as you say its a bit of trial and error...

But food for thought though..

Mark

---
http://www.youtube.com/MrMadjones

http://gw0wvl.webs.com/
20/Jul/2011, 5:46 pm Link to this post Send Email to madmark1   Send PM to madmark1 Blog
 
Ivy Watts Profile
Live feed
Blog
Friends
Miscellaneous info

Freebander

Registered: 05-2011
Location: S. Cheshire
Posts: 70
Karma: 0 (+0/-0)
Reply | Quote
Re: A Wideband Vertical to cover 24.5 to 29.5 Mhz !!


.


Thanks for the response, Mark.

I think I may have found the answer ....; the retailer of my Yeticom Optima pointed me to the article below.

More and more 'Amateur 10M Radios' with coverage from 24 - 30 Mhz are now on the Freeband and Amateur air waves, and all will need a broadband single antenna to cover these frequencies. Could this be the answer? ... It takes a bit of wading through, but makes sense !!

12 - 10 Meter Vertical Antenna Design

73's de

Terence the Terrible (26FB89)

.


---
26 FB 89
Kenwood TS520SE HF Tx
Yeticom Optima 10/11/12 Mtrs Tx
ICOM PCR1000 - 100 Khz to 1300 Mhz Rx
5/8 Wave 'Venom' Silver Rod
Wire dipoles 40/20/15 Mtrs
M0AQC Digital Modes Interface

21/Jul/2011, 2:10 pm Link to this post Send Email to Ivy Watts   Send PM to Ivy Watts Blog
 
madmark1 Profile
Live feed
Blog
Friends
Miscellaneous info

Accomplished DX-er

Registered: 10-2009
Location: Abertillery
Posts: 454
Karma: 9 (+9/-0)
Reply | Quote
Re: A Wideband Vertical to cover 24.5 to 29.5 Mhz !!


HHmmm, Its not for me Terence, It has been designed to cover to many bands and as such it sacrifices gain and gain is what gets you out, I think that you would be better of using just a matcher on your 5/8 ave antenna as it already covers 26 to 29 mhz the matcher would only really be used on 24 mhz, i cant really see the point in having a antenna that covers all these bands if all you really want is 24 to 30 mhz coverage.
it may appeal to others but its not for me...

Thanks for posting it though Terence.

Mark

---
http://www.youtube.com/MrMadjones

http://gw0wvl.webs.com/
21/Jul/2011, 5:52 pm Link to this post Send Email to madmark1   Send PM to madmark1 Blog
 
Ivy Watts Profile
Live feed
Blog
Friends
Miscellaneous info

Freebander

Registered: 05-2011
Location: S. Cheshire
Posts: 70
Karma: 0 (+0/-0)
Reply | Quote
Re: A Wideband Vertical to cover 24.5 to 29.5 Mhz !!


.



Well - I can't understand it !!!

Using the same antenna, and the same 'Good Quality' Power and SWR Meter, and patch leads, I get totally different SWR, Power and Reflected Power readings from the Magnum Delta Force and the Yeticom Optima. Makes no sense at all !!

However, the Magnum was sold on Ebay and needs to be packed and posted, so only concerned with the Optima now.

Guess what? - I have below below 1:2.5 or less over the whole frequency range of the Optima, so will buy a good ATU just to lower the SWR on the extremes of its coverage. It will work fine without, as it is tolerant up to about 1:4, but hey !! at a 1:3 SWR you are losing 25% of your transmitted power !!

Thats 12.5 Watts lost at 50 Watts output !! and that is reflected back into your output transistors, making them (at least damage), hot, and I want mine to last !!

Terrence the terrible

.

---
26 FB 89
Kenwood TS520SE HF Tx
Yeticom Optima 10/11/12 Mtrs Tx
ICOM PCR1000 - 100 Khz to 1300 Mhz Rx
5/8 Wave 'Venom' Silver Rod
Wire dipoles 40/20/15 Mtrs
M0AQC Digital Modes Interface

27/Jul/2011, 11:41 am Link to this post Send Email to Ivy Watts   Send PM to Ivy Watts Blog
 


Add a reply





You are not logged in (login)