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Re: Transmit Loop?
Mike Penkas
¿ªÔÆÌåÓýI have a pic of a 6 foot 3 1/2 in irrigation pipe helically ?wound with 44 feet of 3 inch copper sheet on QRZ? Used a gamma feed.? Q was extreme.? I only had 2khz bandwidth on 75 meters and the ss linear would go into swr shutdown on voice peaks. WA8EBM -------- Original message -------- From: W0LEV <davearea51a@...> Date: 1/22/22 14:32 (GMT-05:00) Subject: Re: [loopantennas] Transmit Loop? They are extremely easy to build yourself.? However, be advised that any mag loop is extremely narrowbanded.? On 40-meters with my homebrew 1-Meter diameter 1/2-inch copper tubing loop, the 2:1 SWR points are about 5 to 8 kHz apart (extremely Hi-Q).? The lower frequencies are even narrower.? The hedge to that is to make the loop larger. ? Also, the tuning capacitor must be a high-voltage unit, preferably, a vacuum variable cap.? One day on the air, we were discussing a mag loop for 630-Meters.? It would have to be huge.? A small loop of 1 to 2-meters in diameter likely would be so narrow that voice communication would not be possible due to the extremely high Q.? Yes, narrower than 2.5 kHz! Dave - W?LEV ? On Sat, Jan 22, 2022 at 11:18 AM Simon <ohhellnotagain@...> wrote: I am afraid i cannot recommend any ( except maybe for the ciro nazzoni, but that¡¯s very very expensive) -- Dave - W?LEV Just Let Darwin Work |
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Re: Transmit Loop?
They are extremely easy to build yourself.? However, be advised that any mag loop is extremely narrowbanded.? On 40-meters with my homebrew 1-Meter diameter 1/2-inch copper tubing loop, the 2:1 SWR points are about 5 to 8 kHz apart (extremely Hi-Q).? The lower frequencies are even narrower.? The hedge to that is to make the loop larger. ? Also, the tuning capacitor must be a high-voltage unit, preferably, a vacuum variable cap.? One day on the air, we were discussing a mag loop for 630-Meters.? It would have to be huge.? A small loop of 1 to 2-meters in diameter likely would be so narrow that voice communication would not be possible due to the extremely high Q.? Yes, narrower than 2.5 kHz! Dave - W?LEV ? On Sat, Jan 22, 2022 at 11:18 AM Simon <ohhellnotagain@...> wrote: I am afraid i cannot recommend any ( except maybe for the ciro nazzoni, but that¡¯s very very expensive) -- Dave - W?LEV Just Let Darwin Work |
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Re: AM frontend overload?
I observed strong intermod spurs from AM BCB stations caused by oxidized contact in my antenna (although not a loop). Copper oxide is a semiconductor.
Cleaned the contacts, and the spurs were gone. 73, Mike AF7KR |
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Re: Transmit Loop?
I am afraid i cannot recommend any ( except maybe for the ciro nazzoni, but that¡¯s very very expensive)
All i have seen are over priced for what they are. Can you make one?? It if done well will out perorm commercial ones and be much cheaper.plus you have bragging rights you did it yourself. Plus not difficult for a low power one. Simon g0zen |
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Re: AM frontend overload?
I guess that's likely. I just looked up. There are 2 broadcasting station with less than 1 mile from my location. They are broadcasting at 1KW during the day time. Only one station is required to reduce power to 60W at night.? I guess the SDR could handle 1KW+60W but not 2KW.
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Re: AM frontend overload?
¿ªÔÆÌåÓýProbably one or both of the AM broadcast stations that are generating the spurious signal decreased power at "sundown" as required by their licenses.73... Randy, W8FN On 1/21/2022 7:35 PM, Kun N7DMR wrote:
And it's my local time 4pm, that AM overload magically "almost" disappeared now. Not sure why. |
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Re: AM frontend overload?
And I didn't touch my SDR or receiver at all. The RFI just magically "disappeared" at around 4pm today.
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Re: AM frontend overload?
And it's my local time 4pm, that AM overload magically "almost" disappeared now. Not sure why.
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Re: AM frontend overload?
¿ªÔÆÌåÓýCheck your loop. Maybe there's something mechanically damaged that's acting as a diode and creating the RF trouble. If the loop has a preamp can you turn it off and see what happens. A broadcast filter would help only if the crud is being generated in your receiver. If it's being made by a mechanical problem in the loop or an external intermodulation source such as a semiconducting joint in something like a chain-link fence or another electronic device that's coupling into the power lines it won't fix anything.73... Randy, W8FN On 1/21/2022 7:16 PM, Kun N7DMR wrote:
It appears today (It could happened earlier but I didn't check). I need to try to turn my loop and see if I could notch them out. It's possible that the wind may have blow my loop into a position that's being overloaded by AM broadcast. I don't know.? Do you think an AM Broadcast filter would help? |
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Re: AM frontend overload?
It appears today (It could happened earlier but I didn't check). I need to try to turn my loop and see if I could notch them out. It's possible that the wind may have blow my loop into a position that's being overloaded by AM broadcast. I don't know.? Do you think an AM Broadcast filter would help?
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Re: AM frontend overload?
¿ªÔÆÌåÓýIt could be receiver overload, but a very severe case. For sure there's intermodulation (sounds like at least two signals). Does the garbage appear no matter where you tune the receiver? If you had an attenuator you could switch in between the antenna feedline and the radio antenna port you should be able to increase attenuation and at some point see a dramatic drop in the garbage if it's being generated in the receiver. If the stuff just gets weaker but doesn't go away, then it's likely some kind of intermod being generated externally.73... Randy, W8FN On 1/21/2022 5:45 PM, Kun N7DMR wrote:
?? (Recording of my terrible RFI) |
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Re: Transmit Loop?
I am also interested in purchase one transmit loop. If there are any that could cover 40-80m and maybe 20-30W. Ideally with remote tuning, so that I could set it up in my attic.
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AM frontend overload?
?? (Recording of my terrible RFI)
Is this AM frontend overload?? What could I do? |
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Re: LZ1AQ choke and feeder length questions please.
On Thu, Jan 20, 2022 at 04:32 PM, Tom Crosbie G6PZZ wrote:
We¡¯re very lucky the UK isn¡¯t crawling with groundhogs, skunks, coyote or muskrat.Agreed, but we still have squirrels, rabbits, rats, badgers & deer. Even crows can be problematic. Rabbits will quite happily chew through anything that looks like grass or plant roots, and for some reason they seem to favour coax that also carrys DC. The squirrels managed to gnaw through the fuel pipes on one car on two separate occasions until the garage fitted some steel mesh, and for some reason the crows took a dislike to the rear bumper, which they kept on having a real go at until we covered it up. Regards, Martin |
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Re: LZ1AQ choke and feeder length questions please.
Everett
Inflation is going silly here.food prices etc soaring..I expect to see fox population decreasing soon.. Some particular fat healthy looking examples around here!! Hedgehogs all gone i am afraid.. Simon g0zen |
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Re: LZ1AQ choke and feeder length questions please.
Hi Tom,
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You Brits don't have any critters left because you eat them all.
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Everett N4CY
In a message dated 1/20/2022 10:32:56 AM Central Standard Time, tom@... writes: ?
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Re: LZ1AQ choke and feeder length questions please.
¿ªÔÆÌåÓýApart from Simon¡¯s suggestion I don¡¯t know what else to say, Fred. Steel pipes? We¡¯re very lucky the UK isn¡¯t crawling with groundhogs, skunks, coyote or muskrat. No doubt someone will post a list of UK vermin I¡¯m simply not aware of. I¡¯ll have a new loop in the garden this time next month and the cables will be exposed so I think I¡¯ll take some precautionary action. ? Tom G6PZZ ? From: [email protected] <[email protected]>
On Behalf Of Fred
Sent: 20 January 2022 16:01 To: [email protected] Subject: Re: [loopantennas] LZ1AQ choke and feeder length questions please. ? Here's what I'm dealing with... photo links below. |
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Re: LZ1AQ choke and feeder length questions please.
Here's what I'm dealing with... photo links below.
There's a creek that run in the area the closer I run cables to it the more I get chewed up. The most wanted list of critters here are Squirrels,Groundhogs,Skunks,Coyote,Muskrat,Fox. The Groundhogs are the worse they do a lot of damage I have taken out a very high number but it does nothing to the population. 73 Fred KB4QZH |
Everett N4CY
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