9.1 unun

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9.1 unun
Topic Started: 20 Mar 2012 - 17:01 (734 Views)
Paul63	20 Mar 2012 - 17:01 Post #1
26 Charlie Tango 780 Posts: 6 Group: Member Member #2,516 Joined: 14-Mar 2012 MANDATORY_Country England MANDATORY_Location sth london MANDATORY_FirstName paul	Hi all I'm about to set up a 9.1 unun with about 41 feet of wire for the antenna.My question really is about the counterpoise have been told to drop 2 lengths of 20 foot of wire which will act as the earth is this correct, grateful for any advice on this thankyou Paul



Cherokee	21 Mar 2012 - 11:11 Post #2
Da Injun Posts: 12,797 Group: Admin Member #6 Joined: 24-Jun 2009 MANDATORY_Country Wales MANDATORY_Location The Vale of Glamorgan MANDATORY_FirstName Steve	Whoa! That's an impossible question with the information you've given. First of all, what frequency(s) do you want to use the aerial on, and is it RX or RX/TX? Let's just clarify a few odds and ends then it might be easier for you to decide what you need: A "9:1 UNUN" is a Transformer. It will change the aerial feed by a factor of 9:1. So, for example, if your aerial has an impedance of 720 then it'll show the radio 80 AFTER the Unun. Or, ideally, if the aerial is 450 , the radio will get the 50 that it wants. But if the aerial was close to being resonant on frequency and was returning, say, 75 , then the UNUN would do more damage than good by changing that 75 to 8 If you're talking about a single band aerial, then the counterpoise should be 1/4 wave of the resonant frequency. For example, if you're building an aerial for the 20m band, then the counterpoise would be about 5.3m (17.5ft) each and it's a case of the more the merrier. But, for 20m, That main element would be better at 13.3m (43.5ft) and WITHOUT the UNUN (lengths specified above are VERY approximate, just for general information) I'm FAR from an aerial expert (actually closer to the "got no damn clue" category than "Knowledgeable" category), but I know we have some properly clever folks on these Forums that can steer you in the right direction.



KieranStoke	21 Mar 2012 - 11:31 Post #3
26 Charlie Tango 544 Posts: 240 Group: MemberAF Member #1,300 Joined: 7-Jun 2011 MANDATORY_Country England MANDATORY_Location Sandbach, Cheshire MANDATORY_FirstName Kieran	As Steve has said need more info really, what bands, if you have a tuner height of the wire etc as that can make a difference to the un un/balun I am no expert but sure we can help



Mark in Essex	21 Mar 2012 - 14:46 Post #4
26 Charlie Tango 037 Posts: 3,570 Group: Global Moderators Member #17 Joined: 22-Jul 2009 MANDATORY_Country England MANDATORY_Location Essex MANDATORY_FirstName Mark	I have used a 9:1 unun in the past for 20m with about 36ft of wire up about 12 ft from the ground, the counterpoise (only 1) was as much wire as i could get staked into the ground, always used with an ATU....was the Snowdonia Unun, not sure of the technicalities of it all....but it worked on 20 and 40m



Paul63	21 Mar 2012 - 19:46 Post #5
26 Charlie Tango 780 Posts: 6 Group: Member Member #2,516 Joined: 14-Mar 2012 MANDATORY_Country England MANDATORY_Location sth london MANDATORY_FirstName paul	Thanks guys yes its for RX/TX let me get this correct I need certain lengths for each frequency or at least a couple of frequency's. Mark in essex post with the wire lengths picture showing 7-29mhz which is 40-10 meter band at only 9 feet of wire is that correct please tell if its wrong. I'm going to be using a TM 440s with built in atu or do I need a external atu plus I cant stick a counterpoise near the house because of the garden patio so is there another option for the earth,thank you for any more thoughts on this. regards Paul



KieranStoke	21 Mar 2012 - 20:55 Post #6
26 Charlie Tango 544 Posts: 240 Group: MemberAF Member #1,300 Joined: 7-Jun 2011 MANDATORY_Country England MANDATORY_Location Sandbach, Cheshire MANDATORY_FirstName Kieran	9 foots too small for 40m, that's only a 1/4 for 11m!



Sam WD40	21 Mar 2012 - 21:11 Post #7
26 Charlie Tango 747 Posts: 734 Group: MemberAF Member #747 Joined: 2-Jan 2011 MANDATORY_Country England MANDATORY_Location Kettering Northants MANDATORY_FirstName Sam	A mate of mine use's my home brew 9:1 with 10mtr of wire either side and it works well for him he live's in some flats where he can't put a ant up so the counterpoise go's down the guttering and the radial up over the roof and he works quite well even on 10w if it dont work for you dont give up with it just try a different layout with it and you should be able to use the tuner in a ts440 with out a problem !



Cozzmik	22 Mar 2012 - 08:37 Post #8
26 Charlie Tango 465 Posts: 2,382 Group: MemberF Member #796 Joined: 16-Jan 2011 MANDATORY_Country England MANDATORY_Location Sevenoaks Kent MANDATORY_FirstName Sam	Relying on the tuner isnt going to make a non resonant antenna resonant as we all know, of course they work but i have many 1/2 wave wires that dont take up much room and they work very well indeed. Cant you try a 1/2 wave wire...?? I know its not what you asked but its an idea Edited by Cozzmik, 22 Mar 2012 - 08:49.



Cherokee	22 Mar 2012 - 13:27 Post #9
Da Injun Posts: 12,797 Group: Admin Member #6 Joined: 24-Jun 2009 MANDATORY_Country Wales MANDATORY_Location The Vale of Glamorgan MANDATORY_FirstName Steve	I think it is probably best to go back to First Principles: What Bands/Frequencies do you want to operate on? How much Power do you want to be able to handle? How much room (length of Garden) do you have? Can you get height on one end, both ends? If so how high? Things like the Snowdonia/ProWhip do work, after a fashion. With a good tuner and a long counterpoise, they'll get you onto most bands from 40m to 10m, but they are a "compromise" aerial. Their claims of being apparently "fully capable" on 80m are pushing it a bit (IMHO) and even with a 94ft counterpoise I couldn't really expect a single, vertical, end-fed wire, in a telescopic fishing pole, to perform at all well on 160m. The word "Compromise" is a specific definition of an aerial that sacrifices performance on one (or a number of) bands in order to force it to work on a larger number of Bands. They are rarely the best solution, but sometimes they're the ONLY solution - and therefore the "best" in that situation. To clarify the "certain lengths for certain frequencies" statement: If you buy a professional HF Vertical aerial, for example the Butternut HF-9V, it will work on nine bands BUT for it to perform at its optimal level it requires multiple counterpoise wires for EACH of those nine bands. (Most professionally produced multi-band vertical HF aerials will be the same, with the exception of the Diamond CP6 which has Ground-planes like a Sirio 827). The most efficient aerial is one that is Resonant for the specific band that you're using An aerial can be made "Multiband" (i.e. Resonant on two, or more, bands) by installing traps. These would recognise certain frequencies and allow them through to use more of the aerial, while other frequencies are restricted to using a shorter aerial that is more suited to their Resonance. So we could have a Dipole that is resonant for 40m, but also has a Trap to make it resonant for 20m. The next stage down the performance ladder is the multiple band aerial such as a Carolina Windom, or a G5RV. These are Compromise aerials but, with a tuner, they perform very well. The bottom of the pile is the pure Compromise. This would be an End-fed wire and includes such things as the Snowdonia and the ProWhip. These rely on a 9:1 balun to trasform non-resonant aerials to something close enough to 50 for a Tuner to handle. I'm avoiding muddying the field with things like Yagis, Delta-Loops, Bambis and other more specialised options. As has been said, many times, with a good enough Tuner you could use a brass bedstead as your aerial for 160m through to 6m. But it wouldn't be the most efficient by a long stretch. So, let's go back to square one: What frequencies do you want to use? If your reply is "Everything, and I have a budget of £40 tops" then a long-wire and a 9:1 balun is probably the best thing for you. But if you can say: "I want to be good on 20m and 40m, and if I can also get 80m or 17m that's a bonus" it is a much more realistic wishlist. IF you have the room for it, and the height, I think something like a CW40 might be good for you (RadioWorks Link). That's good for the 40, 30, 20, 17, 10, 12 bands. You could listen on the other bands (e.g. 80m and 160m) but not TX. Or consider a half-size G5RV.



mu0chn	28 Apr 2012 - 21:55 Post #10
Posts: 3 Group: Member Member #2,127 Joined: 5-Dec 2011 MANDATORY_Country Guernsey Island MANDATORY_Location St Saviour MANDATORY_FirstName Jes	I have used 41' with my 9:1 not from choice but it just worked out that way. I taped the wire to my 12m pole as I pushed it up and when I was fully extended I cut the wire from the drum. I also cut another short length to go to the earth rod. Not sure what length the coax was but I just used the internal tuner of the IC-746 to match it. Have a look at This Edited by mu0chn, 28 Apr 2012 - 21:56.



Ceto	29 Apr 2012 - 23:01 Post #11
Posts: 22 Group: Member Member #2,609 Joined: 29-Apr 2012 MANDATORY_Country England MANDATORY_Location Norwich MANDATORY_FirstName Dave	Paul. A few points to consider. 1. The loss caused by poor SWR can be horrendous, if you are tuning a random length of wire at the radio end of the coax. 2. A 9:1 balun is only a good idea where the antenna is no where near resonance, as that nine to one transformation takes 50 ohms & turns it into a poor SWR, in the same way it tunes a poor SWR into an easier one to tune. 3. The resonance of your wire is going to depend upon the soil & wire length. 4. This type of antenna is best fed from ground level with an earth stake & counterpoises taken from the feed point (9:1 balun,) this is because any length of wire run to an earth stake risks it becoming a radiator. 4. The alternative to counterpoises, is to use a tunable counterpoise. 5. Space restrictions & the design of this type of antenna can make it a good choice for some. But given todays availability of cheapish remote tuners, don't tune it at the end of a long run of coax.



Michael	2 May 2012 - 15:41 Post #12
26CT855 / 30CT555 Posts: 29 Group: MemberF Member #2,536 Joined: 20-Mar 2012 MANDATORY_Country Spain MANDATORY_Location formentera del segura MANDATORY_FirstName Mike	hi i use something similar to jez.10m telescopic fiberglass pole with just over 10m of antenna wire running up inside of pole[keeps water of wire] no problem with high swr when it rains.wire is atached to top of pole with watertight tape.the other end is just proud at bottom of pole at aprox 8inch.conect to 9:1 unun.then i use 10m counterpoise along the ground.that gives me 40m 20m 17m 15m 10m and some success on 11m.so i hope that is some help to you,best regards mike.



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