Re: Wellbrook traced-out loop amp schematics uploaded to Photos
Hi Bernard,
?
If you still need spice model,
you will find "2SK932-23 Model_Rev0" at?
?
https://www.onsemi.jp/products/discrete-power-modules/jfets/2sk932#technical-documentation
?
|
Re: loop material question
Back when I was working with several radio sites, we were using 2" wide flat copper ground strap; because it was supposedly lower impedance than wire ground conductors. [Lightening as you know is NOT a DC impulse.] Mmmm. At what frequencies do flat strap conductors stop being lower impedance than round conductors or vice-versa?
?
On the other hand, flat strap in the open air outdoors would tend to flap and twist in the wind, making it unsuitable for an outdoors antenna.
--
Phil, K0TWA
|
Re: Common_Mode_Chokes Video
The ferrite used all came from digikey and is a product of fairite corporation. The coil I used has 3 rod assemblies inside.
? 1 assembly is made of 1.02 inch diameter beads 1.125 inches long. The other 2 rods are a stack of .736 diameter 1.125 inches long.
40 beads in each rod for a 45 inch long rod bundle. Mix is 75. Total weight is 10.14788 lbs.
? I use polyester printer media cut in strips to string the rods on...then one layer of a clear plastic tape over the beads. The whole stack pretty much fills the pipe and dense urethane foam is in each end cap of the PVC pipe which puts the stack under compression.
?
?2.39 Lbs of # 20 wire on the 2.375 inch outer diameter PVC.
?5.04mh in the audio range with no core.
?331mh with the core installed.
?Q is 362 @ 2.5 kc.
?
?It is a heavy antenna that works well. The winding is secured and ruggedized by using 3 inch diameter marine shrink wrap with a hot glue lining installed with a heat gun.
|
Re: loop material question
john
Go look at Lz1aq website.. much info on there re loop antenna fabrication..plus much much more.
Chavdar is a well know and respected wealth of knowledge.. ie on here one can buy from USA his modded preamps etc. see Everett..
Regards Simon g0zen
|
Re: Common_Mode_Chokes Video
Hi
Just DONT buy on ebay/ preferred vendor from China! ( even if cheap!) Always more expensive but as above..mouser etc.
Simon g0zen
|
Re: loop material question
thanks for all the replies everyone. Much appreciated. I’ve been ruminating on the connection point. Supporting and fabricating the loop is the easy part. I don’t think having a squared off end of loop will be good. Possible I will taper the sheet to a smaller size at the connection. Possibly have multiple bolts or even a bar type connection at the amp housing. So many possibilities. I will just start experimenting and post my results. Thanks everyone.?
john.?
|
Re: Common_Mode_Chokes Video
I stocked up from
Fair-Rite at Mouser about a year ago. Digikey also had them as
well as several other companies.
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/15/2025 3:46 PM, Fred Moore via
groups.io wrote:
toggle quoted message
Show quoted text
Quick Question.? Who do you purchase your 77 and 75
mix from?
Fred
N4CLA
I use 77mix for my AM BCB filters. I have to get some
75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath
of Helene here in Asheville for some natural radio listening
in the middle of the blackout. It was beautiful listening. I
used the 1246 turns of #20 over over 10lbs+ of ferrite 45
inches long into a 33k to 600 ohm transformer into a MM-1
Sound Devices preamp using Sennheiser HD620S headphones. It
was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid
feedback!
?A real bright spot in the disaster! I could also listen
and tell how fast they restored the grid. It was epic. I had
no power for a week and no water for 2 weeks. No potable
water for over a month.
?
?But no AC grid for miles and miles working? Fantastic
for natural radio!!!
|
Re: Common_Mode_Chokes Video
Quick Question.? Who do you purchase your 77 and 75 mix from?
Fred N4CLA
I use 77mix for my AM BCB filters. I have to get some 75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath of Helene here in Asheville for some natural radio listening in the middle of the blackout. It was beautiful listening. I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long into a 33k to 600 ohm transformer into a MM-1 Sound Devices preamp using Sennheiser HD620S headphones. It was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid feedback!
?A real bright spot in the disaster! I could also listen and tell how fast they restored the grid. It was epic. I had no power for a week and no water for 2 weeks. No potable water for over a month.
?
?But no AC grid for miles and miles working? Fantastic for natural radio!!!
|
Re: Common_Mode_Chokes Video
On Tue, Jan 14, 2025 at 06:31 AM, VLF Dilletante wrote:
I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long
Wow. From where did you got that ferrite?
?
73, Jukka
|
Re: Common_Mode_Chokes Video
I use 77mix for my AM BCB filters. I have to get some 75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath of Helene here in Asheville for some natural radio listening in the middle of the blackout. It was beautiful listening. I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long into a 33k to 600 ohm transformer into a MM-1 Sound Devices preamp using Sennheiser HD620S headphones. It was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid feedback!
?A real bright spot in the disaster! I could also listen and tell how fast they restored the grid. It was epic. I had no power for a week and no water for 2 weeks. No potable water for over a month.
?
?But no AC grid for miles and miles working? Fantastic for natural radio!!!
|
|
|
Re: loop material question
If you remember when MFJ first was selling its transmit loops, the short period when these were contemporaneous with the AEA Isoloop, MFJ touted that their loop
was not a flat element, was instead round tubing. Supposedly, the not crowding of the RF currents in the middle of the flat strip, away from the thin edge dimension, was an advantage
of the MFJ antenna. But i don’t believe their ad; this “loss” would be, i think, minor compared to other small transmit loop losses.
-Hue Miller
Newport, Oregon, USA
?
|
Re: loop material question
John, there is nothing wrong with flat material....except dimensional stability and wind loading.? Even for TX, people have used aluminum flashing to build loops (look up "midnight loop").? It's appealing because no special roller dies or welding/soldering are needed.? Maybe there is a small increase in AC resistance (relative to the same width rolled into a tube) due to proximity effects, but this would probably be small even for a TX loop and completely insignificant for RX as others have pointed out.? If you really want to use sheet stock and can form it into a "U" cross-section, or something similar, for mechanical stability, you'd probably be happier with the overall result.
?
Dan - K3GMQ
?
|
Re: loop material question
So the loop would resemble something like . The antenna in the picture is horizontally mounted but can be mounted vertically as well. There are manuals on the web as the Isoloop has not been manufactured in decades. Tubing gives a bit more structural regidity but there is no reason why a flat strip of the proper type of metal cannot work as long as properly supported.
73, kevin kc6pob
On Monday, January 13, 2025 at 05:24:08 PM PST, Superlite via groups.io <superlite17@...> wrote:
It would be left flat. Not tubular. So it would be a circle of 6” wide copper sheet I have a lot of scrap laying around. Mainly my question is does the element need to be round. ?My loop would be more like a tunnel I suppose. Instead of using tubular material I’m going to use flat metal. Wondering how wide would be too wide. I’m pretty much unlimited in the diameter I could make it. Was thinking about staying at 1m-1.5m diameter.?
|
Re: loop material question
It would be left flat. Not tubular. So it would be a circle of 6” wide copper sheet I have a lot of scrap laying around. Mainly my question is does the element need to be round. ?My loop would be more like a tunnel I suppose. Instead of using tubular material I’m going to use flat metal. Wondering how wide would be too wide. I’m pretty much unlimited in the diameter I could make it. Was thinking about staying at 1m-1.5m diameter.?
|
Re: loop material question
Just wondering if using a sheet of material and rolling your own tube would really be any cheaper or provide any significant benefit over just using readily available copper water tubing available at big box stores for like 20 dollars? Or aluminum fuel tubing? (Not sure of the cost)
?
Tom
?
|
Re: loop material question
wow, thanks for all of the replies.?
yes. I could use 16 or 20oz copper sheet or .032 aluminum.?
I see many people modify existing loops to use copper pipe. Is it necessary to use a round material? Does the cross section of the loop material matter on a rx only loop??
|
Re: loop material question
A circle encloses the
largest area for a given length of material, so the largest
received signal. Loops made of wire are generally square for the
simplest support structure. Loops made of tubing can be
self-supporting and are often squares or octagons using 90 or 45
degree elbows to avoid having to bend tubing.? With a metal
shop, you are pretty much unlimited.
On 1/13/2025 4:47 AM, Simon via
groups.io wrote:
toggle quoted message
Show quoted text
Hi
Welcome.
We need much more info on what you intend to make before advice can be reliably given.
Ie.. active pre amped no tune loop antenna,( ie lz1aq type,) high q tuned? Dia of loop, frequencies of interest etc etc.
However, in general there is no such thing as too big a tube diameter.( dia of tube not loop.) Its usually limited by what you have/ can get/ bend/ not worth the effort due to no real world gains, etc.
A name to call you?
Regards Simon g0zen
|
Re: loop material question
It is generally accepted that copper and aluminum are very good conductors of RF currents...
Maybe Dave missed that message & assumed the OP was referring to sheet steel or tin. Regardless, for a Rx antenna, it is of little consequence.
|
Re: loop material question
I'll contribute with my additional question (ouch):
?
When the thing is a small NON-resonant magnetic loop, for RX-only... is the loop material thickness meaningful?
?
73, Jukka
|
Phil
Superlite