RE: [Elecraft] T1 Antenna Considerations
On Sat, 6 May 2006, Steve wrote:
Thom,
Sorry for the delay in reply. I'm catching up on a bunch of email from
several email lists...
The author advocates using a 1/4 wave (less 5%) as a counterpoise for this
antenna.
I agree: this does sound a lot like the W3EDP antenna, which is described
in "Practical Wire Antennas", pg 33 (among other places). In this
reference, the W3EDP antenna is described as an 85' radiator and 17'
counterpoise. Connect both wires at the back of your tuner.
I use a w3edp radiatior length with 1/4 counterpoises for each bandand have
been told my the purists that my adding the counterpoises, it is no longer a
w3edp.
Seems to work...so now I will try the other lengths and see how that works,
since I have lost the end support for the longer wire due to development in the
area.
thanks
In the article "Taming the End-Fed Antenna" ("The Antenna File",
RGSB, pg
118) he looked at this issue by plotting various 1/2 wave
lengths and
proposed the following end-fed wire lengths:
- 26.5m (86.9 ft) for 160 - 10M use
- 15m (49.2 ft) for 80, 40, 20, 17, 15, 12, 10M use
- 10m (32.8 ft) for 80, 40, 30, 17, 15, 12, 10M use
Thom
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RE: [Elecraft] T1 Antenna Considerations
Thom,
Sorry for the delay in reply. I'm catching up on a bunch of email from
several email lists...
The author advocates using a 1/4 wave (less 5%) as a counterpoise for this
antenna.
I agree: this does sound a lot like the W3EDP antenna, which is described
in "Practical Wire Antennas", pg 33 (among other places). In this
reference, the W3EDP antenna is described as an 85' radiator and 17'
counterpoise. Connect both wires at the back of your tuner.
I hope this helps,
Steve
aa8af
> -Original Message-
>
> On Fri, 6 Jan 2006, Michael Babineau VE3WMB wrote:
>
> >
> > Steve Aa8af wrote :
> >
> >
> >> In the article "Taming the End-Fed Antenna" ("The Antenna File",
> >> RGSB, pg
> >> 118) he looked at this issue by plotting various 1/2 wave
> lengths and
> >> proposed the following end-fed wire lengths:
> >> - 26.5m (86.9 ft) for 160 - 10M use
> >> - 15m (49.2 ft) for 80, 40, 20, 17, 15, 12, 10M use
> >> - 10m (32.8 ft) for 80, 40, 30, 17, 15, 12, 10M use
> >>
> >
> > Anyone serious about using end-fed wires needs to read this
> article, IMHO !
> > I have this permanently book-marked in my copy of The
> Antenna File and
> > I have probably re-read it 20 times.
> >
>
> I don't have access to the book. Did it mention
> counterpoises and any suggested lengths?
>
> the 86.9 foot looks like an W3EDZ value
>
> 73,Thom-k3hrn
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RE: [Elecraft] T1 Antenna Considerations
On Fri, 6 Jan 2006, Michael Babineau VE3WMB wrote:
Steve Aa8af wrote :
In the article "Taming the End-Fed Antenna" ("The Antenna File", RGSB, pg
118) he looked at this issue by plotting various 1/2 wave lengths and
proposed the following end-fed wire lengths:
- 26.5m (86.9 ft) for 160 - 10M use
- 15m (49.2 ft) for 80, 40, 20, 17, 15, 12, 10M use
- 10m (32.8 ft) for 80, 40, 30, 17, 15, 12, 10M use
Anyone serious about using end-fed wires needs to read this article, IMHO !
I have this permanently book-marked in my copy of The Antenna File and
I have probably re-read it 20 times.
I don't have access to the book. Did it mention counterpoises and any suggested
lengths?
the 86.9 foot looks like an W3EDZ value
73,Thom-k3hrn
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RE: [Elecraft] T1 Antenna Considerations
On Fri, 6 Jan 2006, Michael Babineau VE3WMB wrote:
Steve Aa8af wrote :
In the article "Taming the End-Fed Antenna" ("The Antenna File", RGSB, pg
118) he looked at this issue by plotting various 1/2 wave lengths and
proposed the following end-fed wire lengths:
- 26.5m (86.9 ft) for 160 - 10M use
- 15m (49.2 ft) for 80, 40, 20, 17, 15, 12, 10M use
- 10m (32.8 ft) for 80, 40, 30, 17, 15, 12, 10M use
hm, 86.9 looks like the length used for an EDP, doesn't it?
Don't have access to the publication, but does he mention a counterpoise(s)
for any of the lengths above?
73,Thom-k3hrn
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RE: [Elecraft] T1 Antenna Considerations
Steve Aa8af wrote :
In the article "Taming the End-Fed Antenna" ("The Antenna File", RGSB,
pg
118) he looked at this issue by plotting various 1/2 wave lengths and
proposed the following end-fed wire lengths:
- 26.5m (86.9 ft) for 160 - 10M use
- 15m (49.2 ft) for 80, 40, 20, 17, 15, 12, 10M use
- 10m (32.8 ft) for 80, 40, 30, 17, 15, 12, 10M use
Anyone serious about using end-fed wires needs to read this article,
IMHO !
I have this permanently book-marked in my copy of The Antenna File and
I have probably re-read it 20 times.
BTW I thought that I would add that this publication is available in
the US
from the ARRL.
Personally I really enjoy RSGB antenna publications. Folks in the UK
and Europe
have had to contend with "small gardens" for quite some time and have
come up
with some very interesting and innovative antenna solutions to fit in
to small spaces.
Michael VE3WMB
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RE: RE: [Elecraft] T1 Antenna Considerations
Hi Martin, You are using twinlead! A twinlead always acts as a transformer we call it lecher system, my dictonary believes you call it the same :-) If you have a given impedance at one end, the impedence at the other end is depending on frequency and length of the Lecher wires. E.G. If the lenght of the lecher wires is exactly an electrically quarter of the wavelength, an open ended twinlead will show a short= Zero Ohms at the other end. Draw the current curve above the wire and you will understand it easier: A halfwave has zero current at the ends (0 current = high voltage = high impedance) and high current in the middle. At any point along the line you will have another impedance, thats the result of the transformed impedance at the feed point. By the way, thats the reason why lots of twin lead frieds use to have a 2-3m extra piece of twinlead in their bag if they are portable. If by chance the impedance on one band is transformed to a value the ATU cannot handle, they make the twinlead a little bit longer with this reserve piece and - bingo- the tuner now can handle the impedance. 72 de Peter, DL2FI www.qrpproject.de > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Martin Gillen > Sent: Thursday, January 05, 2006 7:43 PM > To: elecraft@mailman.qth.net > Subject: Re: RE: [Elecraft] T1 Antenna Considerations > > Hi, Peter. > > Please excuse my ignorance I'm fairly new to amateur radio ;) > > But I have a question: > > > The only reason that the "use the nearby bushes" > > construct now can be tuned by the T1 is that the impedance goes low > > because a part of the antenna is lying "on the floor" now, > giving high > > capacitance against ground which allways lowers the impedance. > > Yes, I understand that; any radiation from the counterpoise > is effectively lost into the ground. > > However another antenna I have used is a 66ft length of wire > at 15feet, fed in the centre with 300 ohm twinlead. > > In this case, the driven half of the wire is still 33ft long > - but I get really low SWR om 20m and have worked DX with it, > > So why does that work? Is the feedline doing something to > help me out here? Or is a dipole just a completely different > scenario altogether? > > Thanks, > Martin. > > > > ___ > Yahoo! Exclusive Xmas Game, help Santa with his celebrity > party - http://santas-christmas-party.yahoo.net/ > ___ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: RE: [Elecraft] T1 Antenna Considerations
As usualy, you did say it better then i can with my restricted english Ron :-) Have seen your mail after I have written my answer but I thing doubling the knowledge makes it stronger :-) Peter www.qrpproject.de > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Ron > D'Eau Claire > Sent: Thursday, January 05, 2006 8:19 PM > To: elecraft@mailman.qth.net > Subject: RE: RE: [Elecraft] T1 Antenna Considerations > > Martin wrote: > > "...another antenna I have used is a 66ft length of wire at > 15feet, fed in the centre with 300 ohm twinlead. > > In this case, the driven half of the wire is still 33ft long > - but I get really low SWR om 20m and have worked DX with it, > > So why does that work? Is the feedline doing something to > help me out here? Or is a dipole just a completely different > scenario altogether?.." > > -- > > You are describing a classic "doublet" antenna, Martin (a > dipole is, by definition, exactly 1/2 wave long and may be > fed anywhere: center, off-center or at the end. The "dipole" > or "two poles" refer to the two electrostatic poles set up at > the ends of a radiator when it is exactly 1/2 wavelength long). > > In your doublet both sides radiate, as you observed. Feedline > losses are relatively low because it is of a relatively high > impedance (compared to common coaxial lines), which reduces > the SWR the feeders may experience under extreme conditions. > For highest efficiency, an impedance in the 400-600 ohm range > is often used. Another disadvantage of twin-lead is that its > electrical characteristics may change significantly with > moisture, snow and ice. True open wire with virtually all air > dielectric is much more stable in that regard. > > In this case the feedline acts as an impedance transformer. > In another post I explained how the famous Zeppelin antenna > behaves with a 1/4 wave feed line transforming the very high > impedance at the end of the 1/2 wave wire to a low impedance > at the rig. > > The same thing happens here, although exactly what the > impedances being 'seen' by the rig are change dramatically > from band to band. Most hams simply add or, if possible > prune, some feeder to find a length their matching network > (antenna "tuner") can handle on all the bands they want to use. > > As the antenna is made shorter than 1/2 wavelength, the > impedance at the center drops very quickly. However, if the > missing length is made up in the length of the feed line > (e.g. a 33 foot radiator and a 33 foot feed line will be very > close to 1/2 wave long on 80 meters) the effect at the > transmitter end will be very small. However, since radiation > from the feedline of a center fed doublet is minimal if > balanced feed is used, the field strength of such an antenna > drops as the radiator part becomes shorter and shorter. It's > not too bad as long as the radiator is at least 1/4 > wavelength long. If I recall correctly, such an antenna is > only about 1 dB > (1/6 of a typical "S" unit) lower than a half wave radiator. > > So a 66 foot long doublet will do a very good job down as low > as 3.5 MHz, especially if the feed line is at least 33 feet long. > > The other issue is height above ground. A horizontal > antenna's pattern is controlled a great deal by the height > above ground in wavelengths. A horizontal antenna about 1/2 > wave above ground is FB for DX with lobes at fairly low > angles for DX that are as much as 6 dB - a whole S-unit - > stronger than you'd get from, say, a good vertical, thanks to > the reflection from the ground helping the signal. As the > antenna gets closer to the ground the maximum radiation lobe > moves more and more vertically until, at about > 0.2 wavelengths above the ground the lobe points straight up. > That's not much good for DX but it's great for short skip > contacts out to about 1000 miles as the radiation straight up > is scattered and reflected off of the ionosphere. Hams > setting up antennas specifically for working other stations > out to about 1000 miles often purposely put them fairly close > to the ground for just that reason. > > Below 0.2 wavelengths, the main lobe continues to point > straight up but grows weaker as the ground losses increase. > > So your 15 foot high 66 foot long antenna was a FB 40 meter > short-skip antenna and it probably got out quite well for > skip out to about 1000 miles on 80. On 20 you start working > more DX with 15 and 10 meters being excellent DX bands for > it.
RE: [Elecraft] T1 Antenna Considerations
Steve AA8AF wrote: Alan Chester (G3CCB)(SK) proposed a solution for the high end impedance of a 1/2 wave antenna. Mr. Chester rationalized that there might be some impedance-friendly length of wire usable for an end-fed antenna that didn't present the tough-to-tune, high-impedance load on a select set of bands. ... -- One way to look at it is that if the end-fed wire is longer than a 1/2 wave antenna, the extra length is simply a single-wire feedline. Of course, the 'feeder' will also radiate UNLESS one manages to match the impedance of that wire (roughly 600 ohms for a typical wire) to the feed point impedance. To do that, you move the feed point for the single wire away from the high impedance at the end and toward the lower impedance (73 ohms in free space) that will be found near the center. At some point that wire will see a good match and it will have no standing waves. No standing waves on even a signal unshielded wire means it won't radiate (ya' gotta have standing waves to make electromagnetic fields). Of course, exactly that was done by the famous Loren G. Windom (8GZ/W8GZ) and is known today as a Windom antenna. That's the REAL Windom, not the modern variations using open wire feeders that are really just off-center-fed doublets. Windom's antenna used a single wire feeder that did not radiate significantly, but it only worked properly at the one frequency at which the feed line was matched to the antenna. Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] T1 Antenna Considerations
Mick,
Alan Chester (G3CCB)(SK) proposed a solution for the high end impedance of a
1/2 wave antenna. Mr. Chester rationalized that there might be some
impedance-friendly length of wire usable for an end-fed antenna that didn't
present the tough-to-tune, high-impedance load on a select set of bands. In
short, he proposed selecting an end-fed wire length in the 1/8 - 3/8 or 5/8
- 7/8 wavelength range, avoiding 1/2 wavelength (or multiples thereof).
In the article "Taming the End-Fed Antenna" ("The Antenna File", RGSB, pg
118) he looked at this issue by plotting various 1/2 wave lengths and
proposed the following end-fed wire lengths:
- 26.5m (86.9 ft) for 160 - 10M use
- 15m (49.2 ft) for 80, 40, 20, 17, 15, 12, 10M use
- 10m (32.8 ft) for 80, 40, 30, 17, 15, 12, 10M use
You can set up a spread-sheet and calculate wire lengths by increments of
1/8 wave, using band centers (or your desired band segment) as a starting
point. Look for wire lengths that don't fall on the 1/2 wave wire length.
For example, a 15m wire is about 3/8 wave on 40M, around 6/8 wave on 20M and
9/8 wave on 15M.
Steve
Aa8af
> -Original Message-
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
> Sent: Wednesday, January 04, 2006 4:02 PM
> To: elecraft@mailman.qth.net
> Subject: [Elecraft] T1 Antenna Considerations
>
> Hello
> I have just received my T1 kit and i notice that under the
> above heading in the owners manual under random-wire antennas
> it states(avoid lengths close to a multiple of 1/2
> wavelength on any band) please can someone explain why this
> is important,also i wish to use this tuner on the following
> bands 20/15/10m so a suggested wire length would be
> appreciated I only have 40ft of space to play with.
>
> Thank you.
>
> Mick M1MGD K2#4785 K1#1532
> G-QRP 11355 ARCI 12343
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Re: [Elecraft] T1 Antenna Considerations
On Jan 5, 2006, at 10:43 AM, Martin Gillen wrote: Hi, Peter. Please excuse my ignorance I'm fairly new to amateur radio ;) But I have a question: The only reason that the "use the nearby bushes" construct now can be tuned by the T1 is that the impedance goes low because a part of the antenna is lying "on the floor" now, giving high capacitance against ground which allways lowers the impedance. Yes, I understand that; any radiation from the counterpoise is effectively lost into the ground. However another antenna I have used is a 66ft length of wire at 15feet, fed in the centre with 300 ohm twinlead. In this case, the driven half of the wire is still 33ft long - but I get really low SWR om 20m and have worked DX with it, So why does that work? Is the feedline doing something to help me out here? Or is a dipole just a completely different scenario altogether? In the case of a dipole, both halves of the wire are driven and contribute to the radiation pattern. Ideally the feedline will have equal but opposite currents in each conductor and will not radiate. This antenna is about a half-wavelength long and has a feedpoint impedance of approx. 73 ohms. The 300 ohm feedline will transform this to a different value (depending on the length), but this will certainly be within the range of a T1 (which should be used with a balun like the Elecraft BL-1, since you have a balanced antenna and the T1 is designed for an unbalanced case). 73, Bob N7XY K2 #3273 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: RE: [Elecraft] T1 Antenna Considerations
Martin wrote: "...another antenna I have used is a 66ft length of wire at 15feet, fed in the centre with 300 ohm twinlead. In this case, the driven half of the wire is still 33ft long - but I get really low SWR om 20m and have worked DX with it, So why does that work? Is the feedline doing something to help me out here? Or is a dipole just a completely different scenario altogether?.." -- You are describing a classic "doublet" antenna, Martin (a dipole is, by definition, exactly 1/2 wave long and may be fed anywhere: center, off-center or at the end. The "dipole" or "two poles" refer to the two electrostatic poles set up at the ends of a radiator when it is exactly 1/2 wavelength long). In your doublet both sides radiate, as you observed. Feedline losses are relatively low because it is of a relatively high impedance (compared to common coaxial lines), which reduces the SWR the feeders may experience under extreme conditions. For highest efficiency, an impedance in the 400-600 ohm range is often used. Another disadvantage of twin-lead is that its electrical characteristics may change significantly with moisture, snow and ice. True open wire with virtually all air dielectric is much more stable in that regard. In this case the feedline acts as an impedance transformer. In another post I explained how the famous Zeppelin antenna behaves with a 1/4 wave feed line transforming the very high impedance at the end of the 1/2 wave wire to a low impedance at the rig. The same thing happens here, although exactly what the impedances being 'seen' by the rig are change dramatically from band to band. Most hams simply add or, if possible prune, some feeder to find a length their matching network (antenna "tuner") can handle on all the bands they want to use. As the antenna is made shorter than 1/2 wavelength, the impedance at the center drops very quickly. However, if the missing length is made up in the length of the feed line (e.g. a 33 foot radiator and a 33 foot feed line will be very close to 1/2 wave long on 80 meters) the effect at the transmitter end will be very small. However, since radiation from the feedline of a center fed doublet is minimal if balanced feed is used, the field strength of such an antenna drops as the radiator part becomes shorter and shorter. It's not too bad as long as the radiator is at least 1/4 wavelength long. If I recall correctly, such an antenna is only about 1 dB (1/6 of a typical "S" unit) lower than a half wave radiator. So a 66 foot long doublet will do a very good job down as low as 3.5 MHz, especially if the feed line is at least 33 feet long. The other issue is height above ground. A horizontal antenna's pattern is controlled a great deal by the height above ground in wavelengths. A horizontal antenna about 1/2 wave above ground is FB for DX with lobes at fairly low angles for DX that are as much as 6 dB - a whole S-unit - stronger than you'd get from, say, a good vertical, thanks to the reflection from the ground helping the signal. As the antenna gets closer to the ground the maximum radiation lobe moves more and more vertically until, at about 0.2 wavelengths above the ground the lobe points straight up. That's not much good for DX but it's great for short skip contacts out to about 1000 miles as the radiation straight up is scattered and reflected off of the ionosphere. Hams setting up antennas specifically for working other stations out to about 1000 miles often purposely put them fairly close to the ground for just that reason. Below 0.2 wavelengths, the main lobe continues to point straight up but grows weaker as the ground losses increase. So your 15 foot high 66 foot long antenna was a FB 40 meter short-skip antenna and it probably got out quite well for skip out to about 1000 miles on 80. On 20 you start working more DX with 15 and 10 meters being excellent DX bands for it. On those bands it is high enough for good low-angle lobes and at that length the pattern breaks up into multiple lobes that show significant gain over a half-wave radiator. When speaking of lobes, keep in mind that the radiation from an antenna is never zero in any direction. There's always some radiation in every direction. The lobes only indicate that some directions are favored more than others. And, as the QRP and QRPpers constantly prove, miniscule signals can work the world under the right directions. That's why even a low antenna like yours can, at the right times, work DX on 40 or even 80 meters. Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: RE: [Elecraft] T1 Antenna Considerations
Hi, Peter. Please excuse my ignorance I'm fairly new to amateur radio ;) But I have a question: > The only reason that the "use the nearby bushes" > construct now can be tuned by the T1 is that the > impedance goes low because a part of the antenna is > lying "on the floor" now, giving high capacitance > against ground which allways lowers the impedance. Yes, I understand that; any radiation from the counterpoise is effectively lost into the ground. However another antenna I have used is a 66ft length of wire at 15feet, fed in the centre with 300 ohm twinlead. In this case, the driven half of the wire is still 33ft long - but I get really low SWR om 20m and have worked DX with it, So why does that work? Is the feedline doing something to help me out here? Or is a dipole just a completely different scenario altogether? Thanks, Martin. ___ Yahoo! Exclusive Xmas Game, help Santa with his celebrity party - http://santas-christmas-party.yahoo.net/ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] T1 Antenna Considerations
Martin, > As previously stated a halfwave end fed wire represents a > very high impedance which is outside of the matching range of the T1. I agree, the impedance hight depends on the capacitive load of the wire ends against ground. > I have found that a halfwave long wire works as long as it is > fed against a raised counterpoise, ie. a wire lying over some > nearby bushes. In this case it works because the two wires > are really an off center fed dipole with the radio in the middle. But if you add any wire length to a Lambda/2 behind it´s feedpoint, the impedance will still be high, you still are feeding at Lambda/2. On a given length of long wire, the impedance is high every Lambda/2 length and low every Lambda/4 length. The only reason that the "use the nearby bushes" construct now can be tuned by the T1 is that the impedance goes low because a part of the antenna is lying "on the floor" now, giving high capacitance against ground which allways lowers the impedance. The worse thing is, that this part of the antenna now also is radiating into ground ;-( To make a t1 work with a halfwave, you may use a 15:1 / 9:1 Autotransformer directly in the feedpoint. A much better way has been published 1928 by the Austrian Radio Amateur FUCHS. He added another half wave to the antenna, but this halve wave is not a wire but formed by a parallel circuit. halfe wave wire_coil | / | / cap= / _ | / / | / /__ 50 Ohm But I agree, this is not a solution for the T1 In Germany the FUCHS ATU is very common in the QRP Area since the German QRP Club published an all band version. 72 de Peter, DL2Fi ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] T1 Antenna Considerations
Hi, Mick. > please can someone explain why this is important As previously stated a halfwave end fed wire represents a very high impedance which is outside of the matching range of the T1. But thats with no counterpoise or fed against a ground stake. I have found that a halfwave long wire works as long as it is fed against a raised counterpoise, ie. a wire lying over some nearby bushes. In this case it works because the two wires are really an off center fed dipole with the radio in the middle. The end fed halfwave wire does have some interesting characteristics and people do use them, for example they are quick to erect DX antennas because they gave a very low angle of radiation. You just have to make another matching circuit to bring the imedance into the matching range of the T1. Check these web pages for details: http://www.aa5tb.com/efha.html http://www.njqrp.org/n2cxantennas/halfer/index.html http://www.angelfire.com/electronic2/qrp/efhwt.html http://hometown.aol.com/n0lx/triband_tuner.html http://www.arsqrp.com/ars/pages/back_issues/2000_text/1100_text/phased.html For excellent antenna information in general try: http://www.cebik.com/radio.html > i wish to use this tuner on the following bands 20/15/10m > so a suggested wire length would be appreciated I only have > 40ft of space to play with. Is that 40ft by 40ft or is it 40ft by 10ft :) ... Are there any trees or other antennas in that space? What kind of contacts are you interested in making? QRP? QRO? Local? DX? One antenna for all bands or separate antennas? For example if you are interested in DX, you can probably fit a full wave loop for 10m into your lot, or even a cubical quad which would give excellent performance. For local contacts you could consiter a doublet fed with twinlead or even a fan dipole fed with twinlead. If it's just a single wire length, are you planning on feeding it at the end? Or in the centre? Against a counterpoise or against ground? For a quick throw-wire I'd use 42 feet with a 14ft counterpoise. Bend the extra 2 or 3 feet at 90 degrees if you have to make it fit into your 40 feet. You could also use linear loading by using twinlead to put up a folded dipole, or many other ideas. Martin. VA3SIE. ___ To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] T1 Antenna Considerations
A half wavelength wire is very high impedance and outside the range of most auto tuners. If you're going to use half wave wires, feed them through a 9:1 current balun. (OK, it's not a balun, it's an impedance transformer) [EMAIL PROTECTED] wrote: Hello I have just received my T1 kit and i notice that under the above heading in the owners manual under random-wire antennas it states(avoid lengths close to a multiple of 1/2 wavelength on any band) please can someone explain why this is important,also i wish to use this tuner on the following bands 20/15/10m so a suggested wire length would be appreciated I only have 40ft of space to play with. Thank you. Mick M1MGD K2#4785 K1#1532 G-QRP 11355 ARCI 12343 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] T1 Antenna Considerations
Hello I have just received my T1 kit and i notice that under the above heading in the owners manual under random-wire antennas it states(avoid lengths close to a multiple of 1/2 wavelength on any band) please can someone explain why this is important,also i wish to use this tuner on the following bands 20/15/10m so a suggested wire length would be appreciated I only have 40ft of space to play with. Thank you. Mick M1MGD K2#4785 K1#1532 G-QRP 11355 ARCI 12343 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
