You at one time sent me several AP models by email, but the PC I was using then crashwd and my email account has been purged either by me or my provider. 
I don't have them anymore...
I don't have them anymore...
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Any Astro Plane Fans ?
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I wondered whether the center frequency could be slid up ordown as with the coventional vertical monopole by this device, or would it require dimensional adjustments to the whole antenna...
I may try to do a 2m version to play with. Would anyone care to come up with comparable dimensions? Could this be tried against the 11 meter dimensions - 11m dimensions X 0.18604651= 2m dimensions centered around 145 Mhz?
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No analyser or bird at this location Eddie so I checked swr bandwidth with my kenwood sw200a meter,
this is where it first reaches 2:1 its still 2:1 a little wider than noted below,
using more than 200ft of RG213 from meter to astroplane with the coupler screwed directly to the radio 2:1 bandwidth is 24.870 - 27.950,
astroplame is about 35ft to bracket & isolated 1/4wave below the hoop,
Minimum vswr is on 26.460 so its way lower than id like it to be,
I think unless somebody can show otherwise that a 1/2wave mast above the isolator causes the least mast current below the hoop and least effect on vswr.
this is where it first reaches 2:1 its still 2:1 a little wider than noted below,
using more than 200ft of RG213 from meter to astroplane with the coupler screwed directly to the radio 2:1 bandwidth is 24.870 - 27.950,
astroplame is about 35ft to bracket & isolated 1/4wave below the hoop,
Minimum vswr is on 26.460 so its way lower than id like it to be,
I think unless somebody can show otherwise that a 1/2wave mast above the isolator causes the least mast current below the hoop and least effect on vswr.
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Homer, I can scale the dimensions off of my 11m A/P model and give you all the dimensions that should be close. You will have to give me a frequency you will center on and the tubing diameters.
You at one time sent me several AP models by email, but the PC I was using then crashwd and my email account has been purged either by me or my provider.
I don't have them anymore...
Try doing a search for the Astro Plane antenna, put Marconi in the name field, and you should find models in my PDF files.
Oh my I was just thinking of doing a mini Astroplane centered around 160.860 as that is the center of the channels I use all the time.
(I wanted to do it in copper water pipe with 100% sweated joints)
In doing some reading I think a 1/2 wave 2 meter is a usable 3/4 wave 70 cm? .
Note brand new newbie to antennas.
Good enough Bob. 3.03 MHz BW at the end of 200' feet of RG213 is probably not bad.
There may be an explanation for the very low frequency range.
The A/P model I just did to Tib2K's specs shows resonance at 27.100 MHz recorded at the feed point. If the antenna is as old as I suspect, then it was probably cut for 23 channels, and this was right in the middle of the band at that time. Does that seem reasonable to expect?
Bob, as noted above Tib2K's dimensions makes my model resonant at 27.100 MHz at the feed point. This antenna is not isolated (ISO). If I ISO it 4" inches at 108" inches below the hoop making my mast inside the antenna 1" x 197" inches...the resonance comes in at 26.7 MHz...a drop in frequency.
How long and at what diameter is your mast in the bottom of your antenna?
I will have to model this situation and see if I can support your claim. I suspect that ISO or no ISO come as a compromise in some way or another.
I use to make the claim that CMC's were not always bad...if you lived in the sticks with nobody within miles to complain.
I had an A99 that acted terrible on the air and neighbors and radio buddies complained of splatter. Otherwise the antenna worked great as best I could tell.
I talked to an tech engineer at Solarcon about this antenna on the phone, asking about CMC on the feed line connected to the A99. He commented, "...CMC could be a curse or a blessing, and some get out of here that work but are not soldered right. He offered to replace the antenna.
So, the center to center of the hub is 6 3/16" inches then. I'll try that and see if it fixes the match to show a better resistance.
Thanks.
I was simply answering a question with something I noticed in the models I made. I to am more interested in the models that match the actual dimensions and need no further modification to match.
I think you can get some variance with this type of adjustment, however, remember that their is also a "loop" that consists of the hoop and the two elements going to said hoop. I would think that you would have to adjust this as well.
The DB
I will scal a model to that frequency and then fix the dimensions and compare that to fixing the dimensions first and then using the scale feature.
Eddie,
i don't know the exact measurements of the mast above the isolator, it was thrown up in a hurry & not as i would usually install an antenna,
its two pieces, 12ft of 1-1/2" tube slotted inside about 7ft of just under 2" tube about 17ft in total,
no idea where resonance is either, only that minimum vswr is lower in frequency than i want, 27.500 would be ideal.
i don't know the exact measurements of the mast above the isolator, it was thrown up in a hurry & not as i would usually install an antenna,
its two pieces, 12ft of 1-1/2" tube slotted inside about 7ft of just under 2" tube about 17ft in total,
no idea where resonance is either, only that minimum vswr is lower in frequency than i want, 27.500 would be ideal.
Which formular do you use to switch frequencys/length, Homer? A friend build a 2 m version of the AP years ago, when i remember correct with good performance too.
I mean he used thin 1/4" cooper pipe what he soldered.
Im very interested in building a 20m version of the AP with an 80 ft mast as base. Should be very funny dx-ing!
Victor
When I rescaled my AP model to 145 MHz the model produced performance just like at 11 meters. When I adjusted the wire diameters to .25" and .125" inch like you mentioned...the model did not like that.
I will try to do some more on it tomarrow.
I have no scientific formula as I am a man of simplicity.
What I did was use an antenna calculator to get the size of a 1/2^ @27.2 Mhz and a 1/2^ @ 145 Mhz.
27.2 = 5.51m
145 = 1.03m
1.03 ÷ 5.51 = 0.18693285
Next I took the dimensions of the Astroplane and multiplied them by 0.18693285.
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