discone antenna
Has anyone of the group ever built or used a discone antenna? I am building one for my son, who recently got his license. I am using the design criteria from the ARRL Antenna Book, 22nd edition. I am designing it to cover the 29 MHz 10 meter FM segment up through ?? however far it will work. It has turned out to be a challenge in that the antenna has to fit through a 24x52 inch opening to the attic of his house. It’s a neat trick to get an antenna to do this with a 6 foot diameter disc and 8 foot diameter cone :-) As usual, the project got a little more complex than I originally thought it would. Don’t they all?!
With luck, I should be able to test it with the analyzer by the weekend. I will let you know the results.
I will probably develop a power point presentation. Is one of the group involved with the hamvention forums? I might be persuaded to give a presentation. The photos are 5 meg files. Too large to post here, perhaps.
At any rate, I would be interested to hear of your experience with this type of antenna.
Thanks & 73,
Dave, K4TO
ps — my son is K4TOO :-)
I've used the commercial VHF/UHF ones from Radio Shack (remember them?),
Diamond, etc., at nearly every QTH I've had.
The SWR sweeps generally show a not-great-but-usable SWR over the wide
range, with fairly sharp dips at a number of places. At least one of
the ones I used had a resonance near 144, 222, and 440 -- I don't know
if that was mere luck, or might have been related to the vertical whip
with loading coil that some manufacturers add to the top to provide "low
band" coverage.
I like to have one available because it gives you at least some
capability anywhere you want to listen (and sometimes talk). I always
assume that the performance will be no better than a 1/4 wave
groundplane, and I'm usually not disappointed. :-)
John
On 2/8/2017 11:22 AM, Dave Sublette via mvus-list wrote:
Has anyone of the group ever built or used a discone antenna? I am building one for my son, who recently got his license. I am using the design criteria from the ARRL Antenna Book, 22nd edition. I am designing it to cover the 29 MHz 10 meter FM segment up through ?? however far it will work. It has turned out to be a challenge in that the antenna has to fit through a 24x52 inch opening to the attic of his house. It’s a neat trick to get an antenna to do this with a 6 foot diameter disc and 8 foot diameter cone :-) As usual, the project got a little more complex than I originally thought it would. Don’t they all?!
With luck, I should be able to test it with the analyzer by the weekend. I will let you know the results.
I will probably develop a power point presentation. Is one of the group involved with the hamvention forums? I might be persuaded to give a presentation. The photos are 5 meg files. Too large to post here, perhaps.
At any rate, I would be interested to hear of your experience with this type of antenna.
Thanks & 73,
Dave, K4TO
ps — my son is K4TOO :-)
mvus-list mailing list
mvus-list@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/mvus-list
Hi Dave
The size of the cone determines the lowest frequency the antenna will work at. How fine you can make the gap between the cone and the disk determines the highest frequency.
One trick used on may of the commercial discones that say 27-15000 MHz is to mount a CB loaded whip in the middle of the disk. So it's really a 27 MHz 100-1500 MHz antenna with a big gap between 28 and 100 MHz.
So if you want to use it on 29 MHz and 2 Meters +, consider taking a few turns off, or shortening the whip on an old CB antenna and mount it in the middle of a more manageable sized discone.
73 Kent WA5VJB
From: Dave Sublette via mvus-list <mvus-list@febo.com>
To: Midwest VHF/UHF Society Mailing List mvus-list@febo.com
Sent: Wednesday, February 8, 2017 10:22 AM
Subject: [mvus-list] discone antenna
Has anyone of the group ever built or used a discone antenna? I am building one for my son, who recently got his license. I am using the design criteria from the ARRL Antenna Book, 22nd edition. I am designing it to cover the 29 MHz 10 meter FM segment up through ?? however far it will work. It has turned out to be a challenge in that the antenna has to fit through a 24x52 inch opening to the attic of his house. It’s a neat trick to get an antenna to do this with a 6 foot diameter disc and 8 foot diameter cone :-) As usual, the project got a little more complex than I originally thought it would. Don’t they all?!
With luck, I should be able to test it with the analyzer by the weekend. I will let you know the results.
I will probably develop a power point presentation. Is one of the group involved with the hamvention forums? I might be persuaded to give a presentation. The photos are 5 meg files. Too large to post here, perhaps.
At any rate, I would be interested to hear of your experience with this type of antenna.
Thanks & 73,
Dave, K4TO
ps — my son is K4TOO :-)
mvus-list mailing list
mvus-list@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/mvus-list
Thanks John. Yes, I think the commercial ones are tweaked to give those dips you saw. I want this one to cover up to 440 MHz FM. Intuitively, looking at the design, it seems to me that shorter “radials”, for lack of a better term, could be added to the top disk and to the top section of the cone to enhance operation at the upper end. The top whip is a “cheater” to lower the frequency coverage at the bottom. I might have made a slightly smaller dimension and stuck a top whip on it, but height in the attic space is just enough to allow a 7 foot tall antenna with a 6 foot disk at the top.
Dave
On Feb 8, 2017, at 11:33 AM, John Ackermann N8UR via mvus-list mvus-list@febo.com wrote:
I've used the commercial VHF/UHF ones from Radio Shack (remember them?), Diamond, etc., at nearly every QTH I've had.
The SWR sweeps generally show a not-great-but-usable SWR over the wide range, with fairly sharp dips at a number of places. At least one of the ones I used had a resonance near 144, 222, and 440 -- I don't know if that was mere luck, or might have been related to the vertical whip with loading coil that some manufacturers add to the top to provide "low band" coverage.
I like to have one available because it gives you at least some capability anywhere you want to listen (and sometimes talk). I always assume that the performance will be no better than a 1/4 wave groundplane, and I'm usually not disappointed. :-)
John
On 2/8/2017 11:22 AM, Dave Sublette via mvus-list wrote:
Has anyone of the group ever built or used a discone antenna? I am building one for my son, who recently got his license. I am using the design criteria from the ARRL Antenna Book, 22nd edition. I am designing it to cover the 29 MHz 10 meter FM segment up through ?? however far it will work. It has turned out to be a challenge in that the antenna has to fit through a 24x52 inch opening to the attic of his house. It’s a neat trick to get an antenna to do this with a 6 foot diameter disc and 8 foot diameter cone :-) As usual, the project got a little more complex than I originally thought it would. Don’t they all?!
With luck, I should be able to test it with the analyzer by the weekend. I will let you know the results.
I will probably develop a power point presentation. Is one of the group involved with the hamvention forums? I might be persuaded to give a presentation. The photos are 5 meg files. Too large to post here, perhaps.
At any rate, I would be interested to hear of your experience with this type of antenna.
Thanks & 73,
Dave, K4TO
ps — my son is K4TOO :-)
mvus-list mailing list
mvus-list@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/mvus-list
mvus-list mailing list
mvus-list@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/mvus-list
Hi Kent,
I always read your posts with interest. As I just noted in my reply to John, We didn’t have enough head room for the top whip. Now — as to the gap between the disc and the cone — that’s good info. I have it at 2 inches now, but I could tweak it down to a half an inch. I think I will leave it at 2 inches for the first test, then reduce the gap and test again. The difference will interesting to see.
Thanks!
Dave
On Feb 8, 2017, at 11:35 AM, KENT BRITAIN wa5vjb@flash.net wrote:
Hi Dave
The size of the cone determines the lowest frequency the antenna will work at.
How fine you can make the gap between the cone and the disk determines the
highest frequency.
One trick used on may of the commercial discones that say 27-15000 MHz is to mount a CB loaded
whip in the middle of the disk. So it's really a 27 MHz 100-1500 MHz antenna with a big
gap between 28 and 100 MHz.
So if you want to use it on 29 MHz and 2 Meters +, consider taking a few turns off, or shortening
the whip on an old CB antenna and mount it in the middle of a more manageable sized discone.
73 Kent WA5VJB
From: Dave Sublette via mvus-list mvus-list@febo.com
To: Midwest VHF/UHF Society Mailing List mvus-list@febo.com
Sent: Wednesday, February 8, 2017 10:22 AM
Subject: [mvus-list] discone antenna
Has anyone of the group ever built or used a discone antenna? I am building one for my son, who recently got his license. I am using the design criteria from the ARRL Antenna Book, 22nd edition. I am designing it to cover the 29 MHz 10 meter FM segment up through ?? however far it will work. It has turned out to be a challenge in that the antenna has to fit through a 24x52 inch opening to the attic of his house. It’s a neat trick to get an antenna to do this with a 6 foot diameter disc and 8 foot diameter cone :-) As usual, the project got a little more complex than I originally thought it would. Don’t they all?!
With luck, I should be able to test it with the analyzer by the weekend. I will let you know the results.
I will probably develop a power point presentation. Is one of the group involved with the hamvention forums? I might be persuaded to give a presentation. The photos are 5 meg files. Too large to post here, perhaps.
At any rate, I would be interested to hear of your experience with this type of antenna.
Thanks & 73,
Dave, K4TO
ps — my son is K4TOO :-)
mvus-list mailing list
mvus-list@febo.com mailto:mvus-list@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/mvus-list https://www.febo.com/cgi-bin/mailman/listinfo/mvus-list
I use a Radio Shack discone weekly for both broadband receive and low power ham transmit through its 25 MHz - 1300 MHz range. I also own and use a military surplus 225-400 MHz discone for receive only. If I could only have one antenna it would be my RS discone!
Michael, N8QHV
On Wednesday, February 8, 2017 11:25 AM, Dave Sublette via mvus-list <mvus-list@febo.com> wrote:
Has anyone of the group ever built or used a discone antenna? I am building one for my son, who recently got his license. I am using the design criteria from the ARRL Antenna Book, 22nd edition. I am designing it to cover the 29 MHz 10 meter FM segment up through ?? however far it will work. It has turned out to be a challenge in that the antenna has to fit through a 24x52 inch opening to the attic of his house. It’s a neat trick to get an antenna to do this with a 6 foot diameter disc and 8 foot diameter cone :-) As usual, the project got a little more complex than I originally thought it would. Don’t they all?!
With luck, I should be able to test it with the analyzer by the weekend. I will let you know the results.
I will probably develop a power point presentation. Is one of the group involved with the hamvention forums? I might be persuaded to give a presentation. The photos are 5 meg files. Too large to post here, perhaps.
At any rate, I would be interested to hear of your experience with this type of antenna.
Thanks & 73,
Dave, K4TO
ps — my son is K4TOO :-)
mvus-list mailing list
mvus-list@febo.com
https://www.febo.com/cgi-bin/mailman/listinfo/mvus-list