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Author Topic: VLF converters?  (Read 27945 times)
K5TED
Member

Posts: 92




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« on: April 18, 2017, 07:08:48 PM »

Looking for some assessments of VLF upconverters vs. VLF bandpass filters for getting away from MW interference on LF/VLF. This is on a variety of radios, ranging from Flex to Icom PCR. The Flex is the most problematic below 500kHz. The Icoms and the Yaesus tune down there and receive OK, but still have lots of interference from local MW.
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VA3VF
Member

Posts: 802




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« Reply #1 on: April 19, 2017, 05:19:34 AM »

A VLF bandpass is likely a good idea regardless of an upconverter, or a receiver that receives VLF natively. Also, Icoms and Yaesus, will likely have much reduced sensitivity in the VLF range. In this case, a VLF upconverter is a better approach.

73 de Vince, VA3VF

Looking for some assessments of VLF upconverters vs. VLF bandpass filters for getting away from MW interference on LF/VLF. This is on a variety of radios, ranging from Flex to Icom PCR. The Flex is the most problematic below 500kHz. The Icoms and the Yaesus tune down there and receive OK, but still have lots of interference from local MW.
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K0OD
Member

Posts: 2959




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« Reply #2 on: April 19, 2017, 08:19:16 PM »

You've probably read my extensive review of the venerable Palomar design and my use of it with my Flex-5000. Oddly that product was recently discontinued, just as we're getting the 600 meter band.
http://www.eham.net/reviews/detail/5541

http://k1el.tripod.com/VLF.html

The $15 Jackson Harbor kit is supposed to be good.  http://wb9kzy.com/lfconv.htm

Last I heard the Heros converter from the UK was still being made for around $300
https://www.herostechnology.co.uk/pages/VLF_LF_Converter.html

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HAMFESTS
Member

Posts: 63




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« Reply #3 on: April 21, 2017, 10:39:15 AM »

Hi K5TED,

Do you want to build your own converter or buy one?

I built this circuit and it worked very well for me. The mixer could be a bit harder to get these days but any input filter that has the same specs could be used instead of the T68-3 cores filter. At least the article gives the inductance values in case other cores are easier to find.

http://www.lwca.org/library/articles/kf5cq/lfconvtr.htm

It's based off the article in June 1977 QST, starting on page 23 A High-Performance Low-Frequency Converter (available in the QST archives)

I have been meaning to build the Amrad converter from QST with the active antenna but time is short so I can't say it's better or not. Too many projects, no time.

I heard good things about the Jackson Harbor too so that would be a good kit to start with.


73
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KB1WSY
Member

Posts: 1282




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« Reply #4 on: April 23, 2017, 06:05:17 AM »

The mixer could be a bit harder to get these days....

Looks like it is still available: https://www.minicircuits.com/WebStore/dashboard.html?model=SBL-3%2B. It is now called the "SBL-3+" but presumably the "plus" model and the old model are compatible.

73 de Martin, KB1WSY
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HAMFESTS
Member

Posts: 63




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« Reply #5 on: April 26, 2017, 02:47:06 PM »

Hi Martin,

You are correct.

It's still produced but ordering from Mini-Circuits might be harder. The minimum order is $50. (some people may not be able to do that. For some reason I thought the minimum was $100 last year). I don't know if they give hams a break with a lower minimum order. (doesn't hurt to ask) The + mean ROHS compliant or just an improved mixer. Some electronics parts places used to have them in single lots.

I ordered some mixers and VCOs last year to play around with and because my prototype from the article worked (I was surprised!) I'm going to build another in a nicer cabinet and better circuit layout with another etched board. I tried a SMT version and it didn't work as well (SMT mixer and components). I may try again with the SMT version but first I need to build the regular version.

One thing that always confuses me is that it's called a "plug-in" but I could never find a socket for it. In anything I've seen they are always soldered on board.

Thanks for the feedback.
73
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K2BIO
Member

Posts: 0




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« Reply #6 on: April 28, 2017, 08:30:57 AM »

A VLF bandpass is likely a good idea regardless of an upconverter, or a receiver that receives VLF natively. Also, Icoms and Yaesus, will likely have much reduced sensitivity in the VLF range. In this case, a VLF upconverter is a better approach.

73 de Vince, VA3VF

Looking for some assessments of VLF upconverters vs. VLF bandpass filters for getting away from MW interference on LF/VLF. This is on a variety of radios, ranging from Flex to Icom PCR. The Flex is the most problematic below 500kHz. The Icoms and the Yaesus tune down there and receive OK, but still have lots of interference from local MW.
Is there any consensus on the performance of the Elecraft K3S vs up converters?
TIA
Don    K2BIO
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VA3VF
Member

Posts: 802




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« Reply #7 on: April 28, 2017, 08:40:49 AM »

I don't have a K3S...I wish.  Wink

If the K3S, like most other transceivers, attenuates signals below 1.8Mhz, a pre-amp would be needed, but you are likely better off with an up-converter.

73 de Vince, VA3VF

A VLF bandpass is likely a good idea regardless of an upconverter, or a receiver that receives VLF natively. Also, Icoms and Yaesus, will likely have much reduced sensitivity in the VLF range. In this case, a VLF upconverter is a better approach.

73 de Vince, VA3VF

Looking for some assessments of VLF upconverters vs. VLF bandpass filters for getting away from MW interference on LF/VLF. This is on a variety of radios, ranging from Flex to Icom PCR. The Flex is the most problematic below 500kHz. The Icoms and the Yaesus tune down there and receive OK, but still have lots of interference from local MW.
Is there any consensus on the performance of the Elecraft K3S vs up converters?
TIA
Don    K2BIO
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K0OD
Member

Posts: 2959




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« Reply #8 on: April 29, 2017, 09:20:15 AM »


VA3VF: "If the K3S, like most other transceivers, attenuates signals below 1.8Mhz, a pre-amp would be needed."

No, it wouldn't. Just turn up the gain a bit. Only time you might have a problem is if you're using a highly compromised antenna, especially an indoor one. 

I monitor worldwide longwave with my 43' ham vertical. Even such a small antenna provides S-9+ band noise. Big deal if I lose 10 or even 20dB. Good longwave reception is about crud rejection, not gain. 
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VA3VF
Member

Posts: 802




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« Reply #9 on: April 29, 2017, 09:29:40 AM »


VA3VF: "If the K3S, like most other transceivers, attenuates signals below 1.8Mhz, a pre-amp would be needed."

No, it wouldn't. Just turn up the gain a bit. Only time you might have a problem is if you're using a highly compromised antenna, especially an indoor one. 

I monitor worldwide longwave with my 43' ham vertical. Even such a small antenna provides S-9+ band noise. Big deal if I lose 10 or even 20dB. Good longwave reception is about crud rejection, not gain. 

Good to hear the K3S gain control is effective. My limited experience with other lower priced analog radios has always been that increasing the gain increases everything, no net gain. Cheesy

73 de Vince, VA3VF
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WA4JNX
Member

Posts: 13




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« Reply #10 on: May 02, 2017, 10:21:11 AM »

If you need a low pass filter to get rid of local MW
interference this will do it:

http://www.universal-radio.com/catalog/filters/1143.html

It is a bit pricey but works like a champ...
and you'll only ever need but one.
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VA3VF
Member

Posts: 802




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« Reply #11 on: July 03, 2017, 06:12:58 PM »

Looking for some assessments of VLF upconverters vs. VLF bandpass filters for getting away from MW interference on LF/VLF. This is on a variety of radios, ranging from Flex to Icom PCR. The Flex is the most problematic below 500kHz. The Icoms and the Yaesus tune down there and receive OK, but still have lots of interference from local MW.

I just found out about this offering on eBay.

http://www.ebay.com/itm/282537940958?rmvSB=true

Anybody has got one? If yes, how does it perform?

73 de Vince, VA3VF
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WA4JNX
Member

Posts: 13




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« Reply #12 on: July 04, 2017, 05:54:59 AM »

Mine shipped yesterday,$105.12 usd delivered.

This is the built and tuned version,10-500 khz.

He offers your choice of Antenna Input/
Converter Output connectors,RCA,BNC or
SO239,no extra charge.

Also a "630m Special" at no extra cost,tuned
at 475 khz for max gain.

And an ELF version,01.-100 khz.

All are available in kit form.

Will let you know how well it performs.
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VA3VF
Member

Posts: 802




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« Reply #13 on: July 04, 2017, 06:04:25 AM »

Mine shipped yesterday,$105.12 usd delivered.

This is the built and tuned version,10-500 khz.

He offers your choice of Antenna Input/
Converter Output connectors,RCA,BNC or
SO239,no extra charge.

Also a "630m Special" at no extra cost,tuned
at 475 khz for max gain.

And an ELF version,01.-100 khz.

All are available in kit form.

Will let you know how well it performs.


Looking forward to your review.

One thing that caught my attention, is that it looks like the designer planned for a long wire antenna only.

73 de Vince, VA3VF
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WA4JNX
Member

Posts: 13




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« Reply #14 on: July 04, 2017, 03:47:29 PM »

I thought about that too but he was agreeable
to virtually anything you want on the antenna
input.
Have a fifty foot end fed wire here thru an
unun...figure the impedance is pretty messed
up anyway at LW from what I've read.
The Jackson Harbor Press converter does well
on it,from WWWB all the way up to the NDB's
around 515 khz.
You know how it is,sometimes this is the best
you can do.
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