Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Best Antenna for Crystal Set Worked All States BC challenge?




 
The AM Forum
November 20, 2018, 07:24:10 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1] 2 ... 4   Go Down
  Print  
Author Topic: Best Antenna for Crystal Set Worked All States BC challenge?  (Read 3479 times)
0 Members and 1 Guest are viewing this topic.
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« on: October 22, 2018, 02:21:45 PM »

Hola!

Need some advice...  I'm building up a loose-coupler crystal set with an antenna matching input.  I'd like to see how many distant Broadcash stations I can tune in over the winter.

Questions:   I will be tuning the complete BC band from 540 - 1700 KHz.   So I need a receiving antenna that can be tuned from the shack, no coax feed.

I have two candidate antenna systems... One, a 190' grounded tower with modest radial system -  and a 100' grounded tower that has an extensive 160M ground system, about 130 radials.  (I don't want to mess with Beverages.)

What would be the best config?...  I can run a single wire to the top of either tower (wire about 300' long) which starts at the shack and is tuned there... and electrically ties in to the top of either tower.  The electrical path starts at the bottom of the tower at zero ohms, goes vertically to the top of the tower and then the wire slopes down at a 60 degree angle to the shack.

I presently have a 75M quad at 190' quad fed with hardline that receives the entire BC band very well despite the swr mismatch and was hoping to do better with the wire/tower matched combo.


Another question: Should I instead make the system ALL vertically polarized by running an openwire match feeding the tower that can be tuned at the shack?  (centerfed vertical dipole)  Considering the better performance of verticals compared to horiz polarization below 75M, since all BC stations are vertically polarized, etc.   Or will the BC station polarization "tumble" and be random when DXing in the BC band like the higher freqs do?

Or would an old fashioned horizontal Hiram "T" top capacitance hat stretched between two towers fed with a single center fed wire work best?



Thanks.

T
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
WD5JKO
Member

Offline Offline

Posts: 1716


WD5JKO


« Reply #1 on: October 22, 2018, 05:58:28 PM »



   Tom,

   Sounds like a lot of fun.....

I have a couple of things to ponder.

If you can use an antenna with directivity to null a strong station on top of a weak one, then you gain an advantage.

I am experimenting with a W6LVP loop inside my garage. On the BC band at night, I see an S9+ signal every 10 Khz across the BC band. That loop has a deep null too when positioned right.

https://www.w6lvp.com/

Just thinking that a mile of wire up 200' will give you too many stations stacked on top of each other. Identifying one from the other mostly impossible. Might be much like CB Channel 19 when the skip is rolling in.

My thoughts,,,

Jim
Wd5JKO
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #2 on: October 22, 2018, 06:48:20 PM »

OK Jim -

Yes, the signal congestion will be intense, especially at night, no doubt.  FB on the loops.

I was thinking I needed a high efficiency antenna because of the crystal set needing all the help it can get. But my experiments are showing that if the set is built right, there is usually plenty of signal to work with. Many of the set designs on the web are duds. There are a handful of good ones - dual stages - that have an antenna tuner loosely coupled to the  diode resonant circuit that works like gangbusters.


Another possibility is to run two antenna wires up in different directions (to two different towers as described) and use a variable phasing network to null out unwanted stations... ala like MFJ does to null out noise.  In the end, all the magic will be done with multiple stages of coils and variable capacitors - no active circuits.  

I will post the schematic of my final design... It will take some time.


T
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
KL7OF
Member

Offline Offline

Posts: 2037



« Reply #3 on: October 22, 2018, 09:36:15 PM »

Tom...You are giving yourself quite a challenge by eliminating beverage antennas for the BC band...I have my best luck sorting out the many sigs on the same freq with beverages....I have only 3 up right now... but there was a time when I had 6 operating terminated beverages and it really helped to sort out the sigs...However I would really be interested in your results with the verticals and especially the one with all the radials....Gud luk ...have fun...remember....nothing exceeds like excess....
.Steve

...
Logged
WA2SQQ
Contributing
Member
*
Offline Offline

Posts: 585


« Reply #4 on: October 23, 2018, 08:30:22 AM »

Tom, I've been DX'ing the BCB since the mid 1960's. You are really setting yourself up for quite a challenge. 3 years ago I bought the "PIXEL" magnetic loop with the intention of using it on 160m. I quickly realized that it performs very well even down to ~ 25khz.  Last year I used it for DXing the BCB band. I live near NYC, about 10 miles from most of the major 50 KW stations. Let's say that my noise level is not quiet. What I quickly discovered is that the deep nulls it was capable of did more to get the DX than antenna gain. Being able to null out one station and wait for another was a huge advantage. I've also used a KIWA loop for ~25 years - good antenna, but not nearly as good as the PIXEL.

BTW, the PIXEL decreased my noise floor by 4 S units - that allowed me to work 26 new countries on 160m that I otherwise would not have heard.
Logged
PA0NVD
Member

Offline Offline

Posts: 366


Nico and Chappie (Chappie is the dog...)


« Reply #5 on: October 23, 2018, 01:50:21 PM »

Here an excellent information how to construct such a loop antenna. In my opinion, the pixel is quite expensive (for me anyway)

https://pa0fri.home.xs4all.nl/Ant/Active%20antenna/Active%20receiving%20%20loop%20antenna%20eng.htm
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #6 on: October 23, 2018, 05:22:53 PM »

Very cool guys -  

Thanks for the info. Yes, I've decided to build up some kind of loop as a result.   Maybe a PVC pipe frame, 4 wire turns (400 uH) 10' square mounted on a 10' tower section with a fiberglass mast, rotator. Gotta figure out the tuning remote.

Question:  Someone wrote that if a loop gets too big, its directivity degrades... is this true?   I would think 10' on the BCB is not too big, compared to a common small 2' loop.

Also, does height above ground play a role?  I could mount is on my 50' tower or use a 10'.  Obviously 10' high would be much easier to test and maintain it.  Another point is that it is vertically polarized if fed on the side vs: horiz polarized if fed at the bottom. Wonder if vert wud be best on the BC band....



BTW, [Crystal SET]  check out this guy's design and YouTube demo. He uses separate modules to move the stage coupling around. Listen to how effective his simple but amazing crystal radio is!!  He obviously optimized his design and even sold 16 on eBay.

https://www.youtube.com/watch?v=c-vtvxskcP0
https://www.youtube.com/watch?v=9J89DGnNcqY
https://www.youtube.com/watch?v=No5th3UurlI


A detailed description:

https://www.ebay.com/itm/Two-Piece-Loose-Coupler-DX-Crystal-Radio-amp-High-Gain-Audio-Amplifier-/151954045960?nma=true&si=4jtjBPxQcJHdDLJG7wTsFh6HMgw%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

SCHEMATIC Below.


Bob / W1RKW sent me a really good website of a guy who builds a lot of crystal sets.   I thought his "HobbyDyne II" was an interesting design.  Lots of ideas there.
http://www.hobbytech.com/crystalradio/crystalradio.htm



T


* Crystal Set 1.jpg (497.75 KB, 1600x1163 - viewed 76 times.)
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
PA0NVD
Member

Offline Offline

Posts: 366


Nico and Chappie (Chappie is the dog...)


« Reply #7 on: October 23, 2018, 07:33:47 PM »

A magnetic wide band loop should have only 1 turn of fat wire or better tube. More turns do degrade the sensitivity due to an increased inductance. Even better a figure 8 loop of tubing. The material losses arn't important, the wire size is in order to lower the inductance. The amplifier should have a very low input impedance. Two of the general purpose amps that I did publish in the tech section with out an input resistance are excellent. Couple the outputs via a balun to the coax and set the current to approx 10-20 mA using 2N2222.
But I guess that you are not allowed to have an active antenna, so I am afraid you have to tune it and need more turns, a completely different approach. Here is a very good article about wide band magnetic loops.
http://www.lz1aq.signacor.com/docs/wsml/wideband-active-sm-loop-antenna.htm
Indeed multiturn NON shielded loops may have degraded paterns due to electric field pick-up
Logged
Tom WA3KLR
Contributing
Member
*
Offline Offline

Posts: 1895



« Reply #8 on: October 23, 2018, 08:21:45 PM »

Hi Tom,

Crystals sets - this is the guy I think of - Dave Schmarder N2DS.  I saw him at a number of hamfests in my area a few years ago.  He told me that with his highest Q coils he was able to separate adjacent channels at the top end of the broadcast band.

http://makearadio.com/crystal/index.php
Logged

73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
W3NE
Contributing
Member
*
Offline Offline

Posts: 139


« Reply #9 on: October 23, 2018, 08:57:53 PM »

Tom -
You might want to try looking for "medium wave dxing" on Google. There is a wealth of practical information there, including audio clips of B/C DX, by individuals and some of the many world-wide organizations devoted to that phase of the hobby.
A loose coupler sounds like the way to go for a crystal set; at a club meeting several years ago, one of the members demonstrated a loose coupler (really loose!) made from PVC tubing with a foundation tube over two feet long, on which one of the two tuned coils could be slid for optimum coupling.

Keep us informed about your experiences!

Bob - NE
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #10 on: October 23, 2018, 10:43:35 PM »

Thanks much for the info and reading material guys!  Yes, Tom - N2DS sure has a big collection of sets he built.

Nico / PA0NVD:  I am intrigued about the tubing loops you suggested and the wideband active small loop amplifier circuit.  I have a lot of aluminum tubing I could use for the loop conductor. If I made an active loop as the web site suggested, how big would you make the loop? The figure 8 configuration sounds like the way to go from what I read.


T



Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #11 on: October 23, 2018, 11:01:36 PM »

Well, well looks like LZ1AQ makes a broadband amp...   and here's a figure 8 loop made out of hardline:

http://active-antenna.eu/

And he sells the broadband amp for 89 Euros:
http://www.creative-science.org.uk/loop_lz1aq.html


http://active-antenna.eu/antennas/

T
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
WA2SQQ
Contributing
Member
*
Offline Offline

Posts: 585


« Reply #12 on: October 24, 2018, 08:12:50 AM »

Tom, I have a very close friend / former co-worker who lives in Japan. He builds crystal radios and recently built one that captures RF and rectifies enough to drive a very low power audio amp (IC) that he discovered. His design criteria was to have a radio that did not require any external power. If you are interested I can reach out  to him. I do know that LITZ wire was responsible for the success of the project.
Logged
PA0NVD
Member

Offline Offline

Posts: 366


Nico and Chappie (Chappie is the dog...)


« Reply #13 on: October 24, 2018, 10:53:16 AM »

Hi Tom
I should start with a figure 8 made of 2 circles of 1 square meter or so or a little bigger. The input impedance of he amp should really be low, close to a short circuit. The general purpose amp I did describe in tech section can do it. When R1 is zero, the input impedance is close to zero as well. And it costs close to zero
In order to have maximum QRN suppression, make a balanced amp from two of those amps using 2N2222. But you can start making just one and grounding the other input, making a unbalanced antenna to start. Than R5 should be 47 Ohms to match the cable
Here are the values.
R1 zero,  R2 1 kOhm, R3 470 Ohm, R4, 470 Ohm, Ropt 220 Ohm, R5 100 Ohm + VCC 12 VDC
Combine the two outputs with a high mu ring core twisted line transformer to get 50 Ohm output.
I should build the amps dead bug method at a non etched piece of PCB in order to get a perfect ground. Build small and decouple the +12VDC with a small 0.1 uF ceramic cap in parallel with a 2 - 5 uF tantalum cap
You can experiment with the value of R2 to get more or less gain.
If every works fine, you can always extend the antenna with two circles more to get a quad. That will lower the noise floor almost a factor 2 more.
Logged
K0ARA
Contributing
Member
*
Offline Offline

Posts: 106


The Bull


« Reply #14 on: October 24, 2018, 11:03:09 AM »

Tom
  This is local to me https://www.midnightscience.net/
  Good Luck I'm sure you will have some success.
Logged

Mike KŘARA                99.9% AM
                 AMI  #1692
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #15 on: October 24, 2018, 01:26:49 PM »

Tom, I have a very close friend / former co-worker who lives in Japan. He builds crystal radios and recently built one that captures RF and rectifies enough to drive a very low power audio amp (IC) that he discovered. His design criteria was to have a radio that did not require any external power. If you are interested I can reach out  to him. I do know that LITZ wire was responsible for the success of the project.


Hi Bob -


Sure that sounds good.  I am still looking for the best design. From what I read, Q is important for xtal sets and they are very unforgiving compared to active device radios. So any optimized designs using Litz wire, etc will be appreciated.  I read that some hi-performance xtal sets use coils Q=1000, so that requires some doing.  "The magic of winding Litz wire?"  


I think I will make the set work on BCB, 160M, 75M and possibly 40M too, since I'm going thru the trouble to make an active broadband loop RX system.  Might put the 2 watt 6AQ5 PW AM rig back on and make the two a pair.


Nico:    Could you give me a link to your 2N2222 design?  I didn't see anything in the tech section with a search, but then, there are 300+ pages and I probably used the wrong search keywords.

So you said the 2N2222 broadband amp can adjust its gain...  I wonder how far down in dB a one meter loop is compared to a 100' wire on the BCB?   If I were able to bring the loop up to unity compared to the wire, that would be nice.


Also, could you explain this a little more? You said:

"If every works fine, you can always extend the antenna with two circles more to get a quad. That will lower the noise floor almost a factor 2 more."

Please describe how you would build this "quad" from the beginning?



And, thank you Bob/NE and Mike/ARA for your info and links.

T




Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
PA0NVD
Member

Offline Offline

Posts: 366


Nico and Chappie (Chappie is the dog...)


« Reply #16 on: October 24, 2018, 03:17:36 PM »

Hi Tom
The design of the 'General purpose RF amp" is in this technical forum, approx number 7 from the top. I will  attache the diagram.
The gain can be set by R2. Higher value, more gain. The limit will be where the amp's bandwidth starts to be lower due to the limited HFe of the 2N2222 or where oscillation may become a problem. If you want more gain with high bandwidth, you can just add an other amp like this at the output of the circuit. When R1 is 47 Ohms, the input impedance is approx 50 Ohms.  The gain is R2/R1. Because the loop impedance is very low (which represents R1), the gain may be very high. If you need more bandwidth at the high side, you can substitute T1, the input transistor, for a transistor with a higher Ft. But the loop may work upto 30 MHz or more as is
In the page   http://www.lz1aq.signacor.com/docs/wsml/wideband-active-sm-loop-antenna.htm  you find the quad of 4 loops. If you have a figure 8, you can add 2 loops more in a figure 8 configuration and connect them as in the above page. You get than a plane with 4 loops instead of 2.   
so it are 2 figure 8 loops in the same plane 90 degrees shifted. That will reduce the noise floor almost a factor of 2. Nice experiment later on to improve the performance a little more without changing the amps.
But you can design step by step, start with a figure 8 and a single amp, than use a double amp wit a ring core power combiner/balun in order to get a balanced loop and not a loop with one side to ground, than add an extra output amp if yo need more gain (which may not be required), than add an other figure 8 to get a quad.
Please keep us informed, nice project. Here in Costa Rica are hardly any AM transmitters anymore. In the evening you hear many south- and centro American and Caribean stations all at the same frequencies it seems. One on top of the other


* GP amp.JPG (377.4 KB, 2592x1944 - viewed 42 times.)
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #17 on: October 24, 2018, 05:30:49 PM »

Thanks again, Nico!

That homebrew broadband amp is simple enuff and will save me 89 Euros...   Grin


OK on the multi section loops.  I'll build something up soon once I decide.


BTW, check out this guy's YouTube demo of his Ham/BCB  CW/AM/SSB  crystal set.  Crude, but still amazing what such a simple set will do.  Getting some good ideas. I'll bet more than a few guys here are starting to feel the wintertime urge to build a crystal set.


https://www.youtube.com/watch?v=uU6dsJOOILQ


T
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
PA0NVD
Member

Offline Offline

Posts: 366


Nico and Chappie (Chappie is the dog...)


« Reply #18 on: October 24, 2018, 07:18:54 PM »

Your project started my interest as well Tom. My first need in my new home here in Costa Rica is a 40 meter antenna. When my shack is ready, I like to build me a crystal set as well. Seems a whole lot of fun.
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #19 on: October 24, 2018, 08:17:31 PM »

Nico,

I just thought of a slick idea.... I wondered how the heck will I know where in the band I am tuning the crystal set?  Well, ya know the last YouTube demo with the guy doing ssb/cw with his external Hartley BFO?   Just mount one of these cheap Chinese $35 DDS 0-40MHz generators (with digital display) into the set and it will make a rock-solid ssb/cw BFO as well as give accurate digital readout to the crystal set!  (listen for the zero beat)  Since it is the only oscillator in the radio, it will make the crystal set CW/SSB stability as solid as an SDR.   Switch it off for AM until needed for freq display.  It will advance as slowly as 1 Hz steps... Grin

DDS:

https://www.ebay.com/itm/AD9850-DDS-signal-generator-module-0-40-MHZ-LCD-PC-control-sweep-function/111865608785?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D3e6b16eeabc348448d2b34f27faf3d3d%26pid%3D100005%26rk%3D4%26rkt%3D12%26sd%3D321418276142%26itm%3D111865608785&_trksid=p2047675.c100005.m1851


Demo using CW/SSB: https://www.youtube.com/watch?v=uU6dsJOOILQ


Cool on the Costa Rica move.  What kind of 40M antenna are you considering?


T
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
PA0NVD
Member

Offline Offline

Posts: 366


Nico and Chappie (Chappie is the dog...)


« Reply #20 on: October 25, 2018, 10:36:54 AM »

Hi Tom
That is a good idea!. I have this unit   https://www.ebay.com/itm/0-55MHz-DDS-Signal-Generator-Direct-Digital-Synthesis-HAM-Radio-VFO-Wireless-MF/172385609520?hash=item2822fba730:g:k9QAAOSwal5YD
and several other units that count frequency for boat anchor receiver read-out.
Take care, they may generate some birdies when close to the coils. So you better put it in a small shielded box made from PCboard or so
I did build a Moxon for 20 meters from 4 Chinese fishing rods. For the 40 meters I did purchase a very nice fiber mast from Spiderbeam in Germany. Good price and excellent quality. It is 18 meters. I will mount a little pulley at the top and hoist a 1/2 wave vertical, slightly sloped to have the base free from the house. That gives a nice low radiation angle. I will feed it at the base with a link-coupled parallel circuit. The feed impedance is approx 3000 Ohms, so no radials needed. I just will put 2 groundstakes as a ground, that gives also some lightning protection.
Along the lower half, i will mount a non-connected wire, a half wave passive radiator for 20 meters, at approx 15 cm distance. That will break the antenna electrically in two at the 20 meter band and I get than a vertical array of two half wave radiators above each other. That results in an radiation angle almost constant from 8 degrees upto 50 degrees, so excelent for DX.
In addition, it has 4 dB more gain over a half wave vertical. The antenna will work without that wire as a full wave vertical for 20, but that gives a high radiation angle, not good for DX. A small disadvantage is that I need to make two link coupled LC circuits at the base, one for 40 and one for 20, relay switched.
An other small problem is that I like to have a motor to hoist and lower the antenna. There are frequent and violent thunderstorms here and I am at a quite open and high spot. Very attractive for lightning.... Embarrassed
Logged
W4WSZ
Member

Offline Offline

Posts: 131


« Reply #21 on: October 25, 2018, 03:17:03 PM »


Hello Tom,
                                                                                                               
 70+ years ago, my first antenna was a short wire connected to the bed springs...worked
great.  I did not have a headset, used an ear piece from the old crank telephone set.

Enjoy the fun.......

73,
Bob, W4WSZ
Logged
N1BCG
Member

Offline Offline

Posts: 614


« Reply #22 on: October 25, 2018, 11:40:38 PM »

Since you’re using a crystal radio, you’re going to need all the selectivity you can get. The loop antenna suggestion is good as it provides some directivity. Adding a BCB varactor for tuning will dramatically improve its performance.

I built one. The varactor diode, an NTE 618, is in series with the loop and physically mounted at the top. A bias voltage is carried through your coax and coupled to the loop at the bottom where the impedance is low. The connection is RF bypassed with a .01 cap and has two 1M Ohm DC coupling resistors in series with each lead of the coax (the diode current is minute). RF coupling is accomplished with a snap-on toroid around the loop near that connection. The secondary is 3-4 turns through the toroid with a DC blocking cap in series (to not short out the bias on the coax).

Tuning is accomplished by inserting 0-9V into the coax at the receiver end. I used a 5M pot, a 1M coupling resistor, and a .01 DC blocking cap.

It’s a lot simpler than this sounds! The pics below show the details for a 160-80M version.


* D13699BD-D960-4443-9EAA-35C9012A7447.jpeg (1565.66 KB, 4032x3024 - viewed 50 times.)

* 2A642913-021D-4FB5-BA3E-CDFEB53D770B.jpeg (899.91 KB, 4032x3024 - viewed 41 times.)

* 3EE50F19-D31E-4682-8AE5-F8C79A8460B5.jpeg (1721.64 KB, 4032x3024 - viewed 39 times.)
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7629


"Let's go sailing, Tommy!" - Yaz


« Reply #23 on: October 26, 2018, 01:45:16 PM »

Interesting, Clark!

So you have a way to tune the loop with a varactor diode instead of using a broadband circuit. Certainly worth trying out.

What I am wondering now is how much effect does the inside house wiring (and aluminum siding, if any) have on the loop patterns and ability to null -  ever tried it outside?

Also, if a loop were ground-mounted outside in the clear, how much better would it work at say 50' off the ground from BCB-40M, remotely rotated?

I decided to put my longwire 250' wire hooked to the top of the grounded 100' tower in the air soon as a reference antenna against any loops that I build.


Nico: Great on your plans for the bigger antennas.  Sounds well thought out.

Bob: FB on your bedspring crystal set. Back in the 60's I found that tapping the metal clip on a landline telephone gave the biggest signal by far... :-)   I had one of those rocket xtal sets.

T




* Rocket Crystal set.jpg (89.49 KB, 693x850 - viewed 30 times.)
Logged

“Remember, remember, this is now, and now, and now. Live it, feel it, cling to it. I want to become acutely aware of all I’ve taken for granted.”  -  Sylvia Plath

Favorite Song - Trololo thru the years:  
https://www.youtube.com/watch?v=IVqUecYGnoM
PA0NVD
Member

Offline Offline

Posts: 366


Nico and Chappie (Chappie is the dog...)


« Reply #24 on: October 26, 2018, 03:03:23 PM »

Hi Tom
I did build an amp and connected it to a simple loop of AWG14 wire, so too thin. Just to see if the amp is stable with this input.
Attached a pic of the amp.
It is completely stable and works quite nice. I didn't try further away from the house yet. very close to the house there is a whole lot of magnetic pollution of switching power supplies, computer, WI-FI system etc, so a lot of birdies and noises.
Seems to work upto 30 MHz with the 2N2222 as expected Underneath the metal roof above the deck I did receive SSB from the USA at 14 MHz


* magnetic loop amp.JPG (2246.7 KB, 2592x1944 - viewed 37 times.)
Logged
Pages: [1] 2 ... 4   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.078 seconds with 18 queries.