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Best Antenna for Crystal Set Worked All States BC challenge?




 
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Author Topic: Best Antenna for Crystal Set Worked All States BC challenge?  (Read 3482 times)
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K1JJ
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« Reply #50 on: October 29, 2018, 01:34:05 PM »

This is getting very interesting!

Funny, cuz when I made the first post, I didn't know there was a REAL official WAS BCB challenge. It was my own idea at the time.  But from the various websites we see it mentioned and it likely has strict rules we will need to follow if we participate in their contest.  (Actually it's "Work as many BCB Stations as you can in a week - anywhere in the world")

I would assume no external battery power is permitted, just RF.  BUT, detecting RF and using it for power is fascinating. It would favor users that are near a big BC station and those in the rural areas would have very little to work with. I have WTIC, a 50KW station 20 miles away that could probably power an audio amp, detector and broadband antenna matcher.... :-)

So my guess is detected RF "auxiliary" power is NOT permitted in the contest due to the unfair advantage for some. But then again, location is different for everyone and will affect their overall results anyway.  We must get the rules and see....  In the end, it's just for personal fun and nobody really cares who "wins."

There's really two projects here:  One is a completely stock, conventional 1N34 detector with sensitive headphones - and the other is doing whatever you desire by hot-rodding the set to suit your drag racing urge in the unlimited class.   Receiving is unique because nobody can see or hear what you are doing, so bending the rules is just fooling yourself.

That said, I'd like to set up an experiment detecting 50 KW WTIC and charging some capacitors to see how much power can be tapped. I need to get up the new wire antenna and build the network first.
 
Clark: OK on the FCC database with field strength, etc.  That will help a lot. We need to find out what the top contesters are using. They most likely have it down to a science. Or, who knows, maybe a verbal ID is required to log it in...

T

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« Reply #51 on: October 29, 2018, 01:53:42 PM »

I'm not seeing how a separate detector circuit for D.C. power would *not* be permitted. Worst case it would generate (pardon the pun) a forehead slap and a "why didn't I think of that!" moment for the competition, who you better hope isn't perusing this thread.

BTW, if you were 1 mile from a 50kW signal, you'd also be at a disadvantage as you'd have plenty of power yet a swamped receiver. A crafty design might combine both circuits using one antenna, or better, see if your diode generates it's own bias voltage since crystal sets produce both an A.C. (audio) and D.C. component.

Bah! I'd just go with the separate circuits fed from a dipole with open wire feeder connected to your "A1" and "A2" terminals. One antenna. Done. Dismiss objections as sore losermanship.

During the 1921 Transatlantic Tests, where amateur operators competed to be the first to span the Atlantic using shortwave frequencies, was it cheating that 1BCG, which was built and operated by pioneering luminaries of radio holding dozens of patents among them and included Maj Edwin Armstrong, was the resounding winner with the most strapping signal? Heck no.

Sheesh.
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« Reply #52 on: October 29, 2018, 02:04:35 PM »

Here are the rules to a sample crystal set corntest.  It seems they divide the competition into many classes:

"All reception must be strictly passive, i.e. no signal power amplification before, during or after signal detection in the receiver, to include active onboard or outboard devices, such as converters, oscillators, "free power" circuits, rebroadcasters, unity gain amps, audio amplifiers, and tuners. Such devices, however, may be used to search for and acquire stations, but in order for the station to count for score, the station must be clearly heard when these devices are not in use."

Full Rules:
http://www.crystalradio.us/crystalcontests/index.htm


These guys seem to be the crystal set "ChannelMasters".   Check out some of the sets these guys have built. I was feeling kinda smug with my xtal set progress -  but not anymore.   Grin

http://www.crystalradio.us/crystalradios/2010-1.htm


T


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« Reply #53 on: October 29, 2018, 02:11:38 PM »

b. Detectors with more than one rectifying junction, such as transistors, JFETs or Mosfets may be used providing they are not used in a manner that will amplify the received signal. This does not prohibit the use of multiple detectors in any series/parallel/bridge arrangement, nor does it prohibit the simultaneous use of more than one receiver and/or antennas.

Looks like you're good to go with the separate D.C. supply receiver except that you missed the contest by 9 years.
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« Reply #54 on: October 29, 2018, 02:16:19 PM »

A-HA!!

The MOSFET detector and bias batteries are permitted as long as they do not produce gain:


b. Detectors with more than one rectifying junction, such as transistors, JFETs or Mosfets may be used providing they are not used in a manner that will amplify the received signal. This does not prohibit the use of multiple detectors in any series/parallel/bridge arrangement, nor does it prohibit the simultaneous use of more than one receiver and/or antennas.
c. Bias batteries are permitted to overcome inherent detector threshold levels, subject to the restrictions on signal amplification of 4.b.


They are 3885 AM HAM friendly:

(5) TWO-WAY SHORT WAVE CLASS (HAM OPERATORS ONLY)
The equipment restrictions for this class are the same as for the Short wave class, except a point is awarded for each two-way transmission. The crystal set is used as a receiver. Tube or transistor AM transmitters are allowed, with power and band usage per FCC regulations. A common Ham AM 75 meter frequency in the Southeast is 3.885 MHz.
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« Reply #55 on: October 29, 2018, 07:08:19 PM »

The MOSFET detector seems to take advantage of using another crystal set so to speak as a power source but rolled up into one using the same single antenna and circuit. It's explained in the link below.  

The author claims a large external antenna is not needed.

http://www.arrl.org/files/file/Technology/tis/info/pdf/culter.pdf

Awesome on the rules, Tom.
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« Reply #56 on: October 30, 2018, 06:13:05 PM »

Wow antennas bring out all the fun! Anybody can build an antenna! They all work minus some decibels or so. Hee.

I am thinking two orthogonal delta loops from the tower. Loops are quieter. With a switch or better yet - a stepper driven driven GONIOMETER at the base. Now you can electrically steer the null.

The mechanical construction involves two orthogonal stator windings, and a rotor winding.

As the rotor turns through 360 degrees two peaks and two nulls will be observed. If you add in a vertical element after, you can resolve the ambiguity and you have just reproduced a 1909 Bellini-Tosi Direction finder!


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« Reply #57 on: October 31, 2018, 08:46:57 AM »

The MOSFET detector seems to take advantage of using another crystal set so to speak as a power source but rolled up into one using the same single antenna and circuit. It's explained in the link below.  

The author claims a large external antenna is not needed.

http://www.arrl.org/files/file/Technology/tis/info/pdf/culter.pdf

Awesome on the rules, Tom.

I shared this with my friend in Japan.He shared some details on the radio he built. This might be of interest to some of you.


 I already built it with purchasing special Zero bias FET ALD110900 directly from TI as per attached photos of my project radio.
This radio, it works fine and have re-generation function in it so that why very good sensitivity.
Sometimes radio start regeneration sound of Pi------- while tuning.

The original circuit which you sent me this time, using one regular bar core while I tested multi numbered core to wish higher gain..
The coil Q wise come out around 500 and it is pretty good for this type radio.
Normal coil can get only 100 to 300 even with spider coil.

Then I found another article of Q1000 coil which using special high Q core, R40C1 type from China.
Then it sudden jumps Q up to 1000 and over.
Unfortunately, Today, there are no sufficient coil Q meter, only a few old one by HP or Yokogawa, some old Heath kit so.

So I decided to build Q-meter myself and measured it.
However, my latest coil with my Q meter designed Q up to 1000 become over scaled.
Too high Q than expected.
So I remodeled my meter to up to 2000Q. And measured again.
It come out around 1500 at highest while BC band, wow! What a Nice high Q coil.
I kept searching nice Q coil and core and found someone up loaded Q2000 coil available…
It seems endless challenge to increase coil Q.…

Now my radio is built up with Q=1500 level coil and Zero threshold FET.
One single coil can very small coil inductance so that I connected 5 series for AM band with 700 PF variable capacitor.
One single coil may be used for up to 3.5MHz  w/ Coil Q over 500-1000.
Maybe my toy equipment, old variable capacitor, my poor design…

Beside I am challenging battery less radio and collect electric energy from the air, from radio signal around.
To do so, I have to reduce power consumption, the ALD110900 is good staff and I could operate radio just in 5 to 10 micro A.
IN my home, I can get around 100 micro A and around 5V from local high power AM station which 200kW and about 20km away.

Now continuing challenging to operate loud speaker.
Lately I found TI made RAIL to RAIL Op-Amp which super low power consumption of just 2micro A while idling.
I built-up it in bridged connected Amp and now operating 4 micro-A(because of 2 IC idling current) idling + actual power input by audio signal and operate in about 100-200 micro A to derive loud speaker.
The Audio Power is just around 1 mW. 
It is very tiny power, but good enough to drive high gain loud speaker with gain of 108 dB/W.

Those 200 micro A makes sometimes distorted since voltage drops much.
So, adding 1F / 5.5V gold capacitor and charged up at night and comfortably operate radio up to 300 micro A peak level.

Thank you very much for your continue support me and have a nice day, good care f you.

Sam





* Crystal radio front face L.jpg (558.3 KB, 2560x1920 - viewed 56 times.)
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« Reply #58 on: October 31, 2018, 12:35:33 PM »

Hi Bob -

Thanks for the article from Sam in Japan.

It seems that Q plays a big role, obtaining 1500Q- 2000Q!   He also uses big C and small L, which we talked about for high Q.  So instead of air-core coil forms we are now talking ferrite.

Here's some on e-Bay showing  1300Q using Litz wire:
https://www.ebay.com/itm/NiZn-Ferrite-Toroid-R40C1-37x23x15-mm-for-High-Q-SW-Barron-Crystal-Radio-Coils-/151443830630


Here's some dialogue from builders about these cores and high Q in general for BCB sets:

http://theradioboard.com/rb/viewtopic.php?f=2&t=5586

I see he is tapping RF for power and using the MOSFET detector.

He mentioned using a regen loop in his set for better sensitivity.  Interesting.

It will take some time to digest all of this to make into a radio - so much has advanced.

T

Pictured - One of the nicest sets built by these guys:




* Nice set!.jpg (150.35 KB, 640x480 - viewed 48 times.)
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« Reply #59 on: October 31, 2018, 01:32:22 PM »

I'm going to ask Sam to join this conversation. Sam is an avid ham and a retired engineer from our microwave oven factory.
Here is two more photos of his radio.


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* CRYSTAL FET RADIO ALD110900.jpg (690.09 KB, 2560x1920 - viewed 50 times.)
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« Reply #60 on: October 31, 2018, 01:37:57 PM »

Hi Tom
He talks about regeneration and sometimes oscillation. That means that he has amplification, which is not allowed in the challenge.
There is also an other FET at Ebay. Lower cost and they claim to be better
https://www.ebay.com/itm/MOSFET-3SK143-Q-3DQ-for-Crystal-Radio-Zero-Voltage-Threshold-Detector/161600513556?hash=item25a0242614:g:YBcAAOSwPhdU3sHm:rk:11:
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« Reply #61 on: October 31, 2018, 02:01:23 PM »

FB, Bob -

Yes, Sam can certainly help us with the latest applied technology.

Nico, looks like the MOSFET detector and the new cores are the ticket:

"This MOSFET 3SK143-Q is in the small surface mount package. It has the code "3DQ" printed on the surface.
Traditional crystal radios are used mineral detector or semiconductor diodes to detect radio signal. In recent years amateurs discover that some “zero-voltage-threshold” MOSFET such as ALD110900 or ALD110800 can substitute the diodes in crystal radio without use a battery, only need to add a coil between the souse gate and ground.
In recent years some Chinese amateurs discover the other kind of  MOSFET - 3SK143-Q can substitute the more expensive ALD110900 and have better performance.
The MOSFET 3SK143-Q is not “zero-voltage-threshold” but very close to, so it still can detect very weak signal and have superb selectivity in the crystal radio. Another advantage is that the output impedance of 3SK143-Q can be as low as 1 to 3 KŮ (the ALD110900 is about 25 to 50 KŮ), so you can directly connect the low impedance headphone to the crystal radio output connectors, don't need to use an impedance matching transformer. With the small Ni-Zn R40C1 Ferrite Toroids you will be possible to make a good performance pocket sized crystal radio."

T
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« Reply #62 on: November 02, 2018, 08:46:02 AM »

I got a response from Sam this morning with more info …

Dear Bob-san,
I checked the forum you informed me and also found you did uploaded my text and photos.
I am sorry, found I made some mistake in it. In regard ALD110900 FET is not a TI made but Advanced Linear Devices Inc.  the OP-AMP I am talking is TI made.
In regards to that 3DQ FET, believe it or not this was a Panasonic semiconductor, an old FET for UHF tuner use sometimes ago. I did tried it too sometimes ago...

In regard micro Watts AMP, it is built on tiny conversion PCB as shown.
You can compare with tiny transistor radio Volume control.
My latest Q1500 coils with ANT and regeneration coupling design.
On the PCB, it has air power collected power supply circuit consist of 2 small brown micro inductor top left part on PCB tuned with fixed and variable ceramic capacitor then rectify by shotkey diode for local strongest station.
Those coil maker, single or double combined and also type of diode will wide vary output voltage and current even with same antenna and ground hooked up. The LED is monitor when tuning, then switched off rest of the time.
Now PCB was redesigned little bit more.

Multiple ALD FET’s can be used for higher gain reception for very weak station.
use switch to make double, triple...   But one thunder storm surge cause damaged those expensive FET's and I lately adding RF chokes to bypass grounding at the gate. Since then no damage occurred.
Above are just additional follow up for my radio project.
Anyway, it is still under going for upgrade and may be no end.....

Thank you very much for your attention and good care of you.
Good night from Nara-Japan.
 Best 73 and FB DX. TU..
Sam



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* SAM Over all design L.jpg (423.38 KB, 2048x1536 - viewed 51 times.)
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« Reply #63 on: November 02, 2018, 10:22:04 AM »

Hi Tom
You really started a nice thread Tom, its becoming very interesting!!
I did some calculations and test and like to share some thoughts with you. I put my idea of a design below and appreciate comments. In my opinion he designs with the loose coupler are close to the optimum
In order to extract the energy out of the resonating circuit, the loaded Q should be approx 4 times less than the unloaded Q. When a resonance circuit has a Q of 1000 and you load it down to 500, that means that 50% of the energy is lost in the circuit, that is not what you want, you want it out of your detector.
So a single LC circuit wit a Q of 1000 loaded down to 250 will give you most of the energy with a bandwidth of approx 4 kHz.
A big problem will be adjacent transmitters, interference, so you want a better adjacent channel suppression.
The best answer will be in my opinion a bandfilter design. That gives  however a more difficult tuning especially with the high Q circuits.
A band filter design needs two circuits with the same Q in order to have the best curve.
When my shack is ready, I like to build a bandfilter receiver with one double capacitor for ease of tuning and a fine tuning for one or both circuits to get a perfect tracking
The two circuits will have an adjustable coupling to get a QxK = 1, you can peak the signal with fine tuning and the coupling.
That was done correctly with the loose coupler designs. But the coupling of ring core coils can be realized as well with small variable top capacitors.
The load of the circuits should be so that the loaded Q is approx 250  for circuits with an un-loaded Q of 1000, so an adjustable antenna coupling and adjustable load to the detector are required. The antenna coupling can be a series  capacitor for long antennas, the detector load has a lower impedance and may be realized with switched taps at the LF transformer.
In addition some parasitic circuits can be made to notch-out big disturbing signals
As you see, except the double capacitor with fine tuning, this is the loose coupler receiver!!!
The detector should be a zero bias FET, eg the 3DQ
Please comment what you think of the above Tom
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« Reply #64 on: November 03, 2018, 12:07:40 AM »

Very good, Nico -

Interesting on the Q loading.  If I were to stick with coils made of Litz wire that are on 4" ABS, can I get Q=1000 and see performace approaching the ferrite core coils?  I prefer to stay with the air wound coils for a few reasons.

OK on using the dual bandpass filters with two similar Qs for best coupling and selectivity with the smaller fine-tuning cap.  I plan to put together a system similar to this crystal set in the link below. Who knows, I might add two variable bandpass filters tuned off seperate sections of the same 365 capacitor as you suggested.   The air coils make it easier to experiment with.

https://hackaday.com/2016/09/16/high-performance-crystal-radio/

What circuit do you suggest for a variable parasitic trap?   Maybe a parallel resonant circuit  in series with the antenna input area?

The 3DQ sounds good as a detector.

I am still reading and deciding what to do, but I like the layout and "experimentability" of the set linked above.  (notice how "Moon River" by Andy Williams plays... beautiful example. Listen at 8:55 in video)

Thanks again for the info and advice, OM.

T

This is my current building goal:


* Nice Set.png (321.09 KB, 800x350 - viewed 39 times.)
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« Reply #65 on: November 03, 2018, 12:18:42 AM »

Sam-san,

I appreciate your taking the time to post your comments and experience. Yours is an advanced set that we will be looking closer at as we progress.

Your info about the R40C1 type cores from China is encouraging for high performance.

I will study it more and have more questions later.

Feel free to comment on any of the posts to date.

Thanks again and greetings to you in Japan.

Tom, K1JJ
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« Reply #66 on: November 03, 2018, 09:26:46 AM »

pocket sized crystal radio."
T
Tom-san, you've reminded me of the rocket crystal radios I saw as a kid in the late 1950's; a cousin of mine in Ohio had one, but no one in my 'hood ever had one to play with.

http://www.crystalradio.net/misc/rocket/index.shtml

(Other info on this guy's site also.)
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« Reply #67 on: November 03, 2018, 09:41:23 AM »

would it be possible to use 2 detector diodes in a voltage doubler arrangement expect it to work and would there be an improvement in audio output?

i'm still gathering materials but will give it a go at some point.

update: I think I found my answer. There's no free lunch.
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« Reply #68 on: November 03, 2018, 10:15:32 AM »

Hi Tom
The set with the cylindrical air coils seems very nice to me. You can choose between cylindrical or spiderweb coils. I suppose that the difference isn't that big.
I guess that you can approach a Q of 1000 when wound with litz wire. It is easy to vary the coupling by turning one of the coils. The traps can be made of single LC resonance circuits coupled loosely with the antenna coil. So, if you make the position of the antenna coil fixed, you can place the detector coil at the right side rotatable and the trap coil at the left side rotatable.  The antenna coil and the detector coil will form the band filter. I should start with a distance between the coils the same as the diameter. Prevent capacitive coupling, let the cold sides of the coils face each other. A shield mate of wires at a distance of approx 1/4 - 1/8 inch connected to ground at one side is a very good manner to prevent capacitive coupling. The coupling is VERY loose for good filter aciton if the circuits are loaded correctly, only 0,2 - 0,3 % !!
You can estimate the Q by loosely coupling a generator into the antenna, e.g via 1 pF or less, peaking everything making the coupling between the detector and the antenna coils as lo as possible and measuring the 3dB bandwidth. When you couple a bit tighter, you should get two peaks, the filter is over-coupled. When both peaks are similar in amplitude, the Q of both circuits is similar.
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« Reply #69 on: November 03, 2018, 05:33:38 PM »

Bob/W1RKW discovered the mother of all old buzzard radio suppliers.   This guy has cornered the market on 1920's parts. Prices are quite reasonable.

Think I'll buy a pair of 1920's headphones for the "unamplified" crystal set mode.  Take a look at the knobs offered. Unbelievable selection across the board.

http://www.oldradioparts.com/index.html


T


* Crystal Set Headphones.jpg (28.94 KB, 600x333 - viewed 39 times.)
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« Reply #70 on: November 03, 2018, 06:56:02 PM »

T, the pair on the right is very similar to the pair Gary sent me.  They're almost like new despite a layer of dust.
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« Reply #71 on: November 04, 2018, 12:32:53 AM »

Tom-san, you've reminded me of the rocket crystal radios I saw as a kid in the late 1950's; a cousin of mine in Ohio had one, but no one in my 'hood ever had one to play with.

http://www.crystalradio.net/misc/rocket/index.shtml

(Other info on this guy's site also.)

Tom-san,

That's another great website. Mucho crystal radio info.

The Rocket Crystal Radios:  I had one in the early 60's. I could only hear ONE station on it; WDRC 5KW that was about 1 mile away.  My older brother told be the rod adjustment at the top was the volume control... :-)    That's all it did was make WDRC louder or weaker.   So much for selectivity.

Today I got the new reference BCB receive antenna finalized and connected to the shack. I measured it as 250' of wire strung between the 50' and 100' tower tops with the 100'er grounded to a radial field. It's like an end-fed electrical 350' long wire grounded at the opposite end. Can't wait to try that out.   The loop antenna will have to wait until I build a working crystal set first.

Now that the outdoor work is finished I can play inside as the colder WX moves in..

T
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“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

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https://www.youtube.com/watch?v=IVqUecYGnoM
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"Let's go sailing, Tommy!" - Yaz


« Reply #72 on: November 04, 2018, 10:53:10 PM »

Update on progress:

Good news: I tried out the new BCB 350' long wire / tower antenna.   I built up a C-L  network (1200 pF variable to ground in series with a coil) fed against ground and connected the FT-1000D. I was able to get sharp antenna tuning peaks.   I was using the 50 ohm RX input into the FT-1000D.

I compared this antenna to my two best dipoles. One was the 160M dipole at 190' fed with hardline.  The difference was 10-20 dB on most stations between 540 - 1710 KHz in favor of the long wire.  I'm sure most of this difference was due to the perfect match of the LW compared to the dipole resonant on 1850.  But still, the peak is sharp and I now have signals on AM coming in 55 over compared to much less before. Good place to start with the crystal set experiments.

It even received well on 160M and 75M for locals once matched - compared to optimized coax-fed dipoles. There is a combination of horizontal and vertical components in the various patterns.

T
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“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
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"Let's go sailing, Tommy!" - Yaz


« Reply #73 on: November 11, 2018, 01:50:33 PM »

This is the crystal set we will be building. It's called the Lyonodyne 17. The designer, Mike Tuggle, is well known in the radio hobby world and has been improving it since 1974, thus model 17. He's won several DXing awards with it -  and I like what I see.

Question:

Notice the two traps, trap 1 and trap 2.  These "QRM" traps are supposed to be tuned to the adjacent frequencies to suck out the big stations causing problems to the desired center frequency.  For example, listening to 1100 KHz, traps would be set to 1090 and 1110 to suck out / reduce these offending stations.  (parallel resonant circuit loosely coupled)
  
http://www.crystalradio.net/crystalsets/lyonodyne/index.shtml


Now a different radio (The Moon River" guy) we had considered uses the same circuit (parallel resonant circuit loosely coupled)  and in this case there is only one and he calls it a bandpass filter to peak the desired signal.  These circuits appear to be in the same position and both wired the same - but do opposite functions.

(Goto 3:52 in video demo to see BP filter work)
https://hackaday.com/2016/09/16/high-performance-crystal-radio/


I would think these circuits would peak the signal they are tuned to, broaden out the bandpass when tuned to different frequencies - not suck it out like a classic trap does.     Can someone can explain what is happening here ??

The only explanation I see is that the traps are dropping the offending signals across them and not feeding them forward into the diode circuit.  But then in the other radio acting as a bandpass filter, there is only one path into the detector?  The coupling arrow directions are confusing me - are they significant?


BTW, anyone have a mini UTC A-27  inter-stage audio transformer to sell?   (or equiv  -  T1 UTC A-27: input transformer --100 k-ohm primary; secondary taps, 50 to 600 ohms)


T
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“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
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« Reply #74 on: November 11, 2018, 03:57:17 PM »

Hi Tom
The second receiver does not have traps. The intermediate circuit resonates at the receiving frequency forming a band filter with 3 tuned circuits in stead of 2. That will be quite sharp, but it will be more difficult to get a reasonable pass-band curve because the tuned circuit in the middle is un-loaded. and has a different Q than the antenna circuit and the detector circuit.
I should choose the other design with traps, that gives you more flexibility to notch disturbing signals wich may be the biggest problem.
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