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New Band LF Coming




 
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WU2D
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CW is just a narrower version of AM


« on: February 20, 2012, 09:03:57 PM »

I am building a Class E CW / Beacon rig for the new (coming soon) 600 Meter band.

Itís official ó delegates attending the 2012 World Radiocommunication Conference (WRC-12) have approved a new 7-kilohertz-wide secondary allocation between 472-479 kHz for the Amateur Radio Service. http://www.arrl.org/news/amateur-radio-gets-secondary-mf-allocation-at-wrc-12 It will take a while before the FCC adopts, but it is likely to be a small band to start and limited to 5W EIRP. The new allocation calls for a worldwide secondary allocation to the Amateur Service at 472-479 kHz.

This may not seem like much power but based on the experiments that I did in the 1990's on 180 kHz with 1 W INPUT POWER for microWatts of EIRP based on the Part 15, 50 FT antenna limitation, the band should be quite effective at this power level. I could pick up my beacon easily 35 miles away in my car with an active whip.

Assuming an average vertical antenna of 50 ft with 16 radials (base loaded) to have a gain of -15 to -20 dBi. You would need a transmitter of 100 to 500 Watts to be able to produce this effective power level. 


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Steve - K4HX
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« Reply #1 on: February 20, 2012, 09:11:35 PM »

Hmm. I wonder why 5 W ERP. The experimenter groups that have been on there for quite a few years now have much higher allowed ERPs. The ARRL/WD2XSH crowd got only 20 Watts ERP, but others, including several AMers have authorization for 200 Watts. The FCC just granted an experimental authorization for 500 Watts ERP.
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KM1H
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« Reply #2 on: February 20, 2012, 09:22:34 PM »

The experimental stations werent under any ITU restrictions and the FCC can change the 630M ham band power rating next year on their own.
Several licencees had 1000W authorization, it was just the ARRL affiliated WD2XSH that had a 20W ERP restriction BUT we could operate 470-515KHz with a gap around 500.

Ive been down there for about 2 years now as WD2XSH/39..on CW of course Shocked
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WU2D
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CW is just a narrower version of AM


« Reply #3 on: February 20, 2012, 09:32:07 PM »

Of course I want to build a transmitter:

I have a nice test circuit working with a proper Mosfet driver at 500 kHz and a pair of HV power supply Fets.

I obtained some nice sized low frequency Ferrite toroids, FERROXCUBE T39/20/13-3C85 FERRITE CORE 39mm 20mm 13mm, and swept them and found them to be lossless between 200 and 700 kHz. I did this by putting 5 bifilar turns on and a 50 Ohm load off my generator and sweeping the output. Assuming that I use a pair of Mosfets in Class D P-P and I want to transform up to 50 Ohms.

I am trying to figure a place to start on the turns and the ratio. I need to estimate the minimum impedance needed for each device (each side of the CT) and the step up ratio I need. I would like to try say 10T CT on the primary and 20T on the secondary to start.

My operating conditions for 100W would be 48 VDC and roughly 2.5 Amps.

Mike Wu2D


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Steve - K4HX
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« Reply #4 on: February 20, 2012, 09:32:56 PM »

Yep, ARRL - always the pissweakers.  Sad
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N4LTA
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« Reply #5 on: February 21, 2012, 09:50:43 AM »

5 Watts eirp is not that bad. It should be a great band for the experimenter types and devoid of appliance operators. The limit was because many Mideast couuntries have navagation beacons as primaries in that frequency band. Countries near that area will be limited to 1 W  eirp.


I had just applied for an experimental license in that band 2 weeks before the announcement and had asked for 8 W erp. Don't know what will happen with that.

Pat
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Bill, KD0HG
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« Reply #6 on: February 21, 2012, 07:24:50 PM »

All you need is an ART-13 with one of these LF VFOs installed.
The O-16/ART-13 will give you 200-600 Khz coverage.
The 813 ought to provide enough mojo for the task at hand..


* lf vfo art13.jpg (35.04 KB, 481x301 - viewed 370 times.)
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N4LTA
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« Reply #7 on: February 21, 2012, 08:32:33 PM »

Most LF dx is done with signals many dB below the noise level and filters a few hertz wide. You need a very stable transmitter and receiver. Many guys lock there transmitter and receivers with a Cesium or Rubidium frequency source to work with the narrow filters.

An ART 13 would be good though for local work but the band will be too narrow for much AM work if it is even permitted.

Pat
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WU2D
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CW is just a narrower version of AM


« Reply #8 on: February 22, 2012, 07:22:00 PM »

KW1I actually used an ART-13 for his CW station on the 500 kHz band for a while using the low frequency plug in which is crystal controlled - It did work. Crystal control on a tube rig is technically stable enough for the conventional narrow modes but perhaps not for the exotic below noise coherent modes. It did produce some amazing DX.   
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WA1GFZ
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« Reply #9 on: February 22, 2012, 07:56:27 PM »

Luh=4R(primary)/6.28*F(MHz)
final R primary resistance in ohms

I worked some stations on 600m this past summer running 60 watts into a 200 foot inverted u WE2XGR/8 & /9
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W2PFY
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« Reply #10 on: February 22, 2012, 09:13:38 PM »

For those of you that plan to operate on this new band, perhaps you could let the rest of us know what gear you will use and also include your antenna scheme. I have a 1941 Halstead transmitter that will go down there and in fact, it will operate from about 200 to 500 kHz.
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Bill, KD0HG
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« Reply #11 on: February 22, 2012, 09:14:40 PM »

It would be fun to just run CW there, forget about all of the fancy detection schemes. It's amazing to hear how far the navaids and beacons down there can work with just 25-100 watts into a short vertical. I hear them up to a thousand miles out. Once, even a 100 watt beacon in Ontario, 1,200 miles out.

I am thinking of homebrewing a transmitter or using the ART-13 into the Beverage. Got a homebrew transverter for 160 that could be modified for LF SSB. Pair of 6146s. Would be receiving on the R-389.

Bill
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Pete, WA2CWA
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« Reply #12 on: February 22, 2012, 10:25:59 PM »

With only 7 KHz to play with, I suspect the FCC will limit activity to CW and/or narrow bandwidth data modes but time will tell how fast the FCC even acts on it. Maybe they'll channelized this band too. It will be interesting to see how the major manufacturers will design in this new band into their new equipment.
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Bill, KD0HG
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« Reply #13 on: February 23, 2012, 09:22:23 AM »

The regulations should include "Homebrew Only", Pete.
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KM1H
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« Reply #14 on: February 23, 2012, 09:32:41 AM »

I hope the manufacturers publish info on how to unlock the TX function. Since the RF cant get past the filtered stages it would have to exit via the transverter port or a new hole at the typical pre-driver level of 10-200mw of Class A.
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N4LTA
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« Reply #15 on: February 23, 2012, 10:18:53 AM »

I have a pending experimental license and was planning a 10 meter high vertical woth a large capacitive hat and building a variometer for matching. My plan was to use a 400-500 watt class D transmitter that I am designing now. The 7 Khz wide band will probably be limited to cw and digital. I will use my current Clifton Labs active antenna. I often hear NDBs over a thousand miles away at night in the winter - so CW would be lots of fun with5 W EIRP. During daytime - NDBs at 200 miles can be heard.

To hear properly - you will need a good Rx antenna - preferably with common mode chokes located away from the house to get rid of the electrical  noise generated in most houses.

I now use a R75 with a receive upconverter with a SBL-3 mixer and crystal oscillator, but I am working on a H mode mixer with a TCXO rated at 100 ppb stability. All this new SMT stuff is about to may me blind (or make me realize that I am slowly going blind)

Pat
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WD8BIL
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« Reply #16 on: February 23, 2012, 10:27:54 AM »

Don't worry, Carl. It won't be long before you'll be able to find that on the internet. It only took me 30 minutes to find the info for my IC 718 and get it on the WARC bands.

Power out at 1MHz was about 25 watts!

KM1H said:
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I hope the manufacturers publish info on how to unlock the TX function. Since the RF cant get past the filtered stages it would have to exit via the transverter port or a new hole at the typical pre-driver level of 10-200mw of Class A.

 You can find just about anything on the WWW!
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Pete, WA2CWA
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« Reply #17 on: February 23, 2012, 11:00:40 AM »

Don't worry, Carl. It won't be long before you'll be able to find that on the internet. It only took me 30 minutes to find the info for my IC 718 and get it on the WARC bands.

Power out at 1MHz was about 25 watts!

KM1H said:
Quote
I hope the manufacturers publish info on how to unlock the TX function. Since the RF cant get past the filtered stages it would have to exit via the transverter port or a new hole at the typical pre-driver level of 10-200mw of Class A.

 You can find just about anything on the WWW!

I assume you mean 60 meters and not the WARC bands.

Most of transceivers on the market today have terrible receivers below the broadcast bands and some good front-end filtering will be necessary. Converting a rig for 60 meter transmit coverage probably is a lot easier then trying to roll transmitter circuits and various RF bandpass filter circuits from the current lowest frequency of 1.8 MHz all the way down to 479 KHz.

Time will tell how the manufacturers address it, but personally, I'm not too excited about it. Don't have any transmitters that cover it, don't have enough yard space for an antenna, and the pay-back reward of operating there seem to be minimal at best.
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WU2D
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CW is just a narrower version of AM


« Reply #18 on: February 23, 2012, 08:27:54 PM »

The typical setup is either a homebrew or one of the many commercial or Kit LF converters which typically take 50 to 500 KHz and up-convert to a higher band. I made mine with a Low pass filtered  cascode amplifier into a passive double balanced mixer hooked up backwards ( IF output as the input and RF input as the output). The LO was a 4 MHz crystal. Now this would tune from 10 kHz at 4.010 MHz to 500 kHz at 4.500 MHz.

I also built a portable single conversion superhet receiver that upconverted 100 to 200 kHz to a 4 MHz IF and used 4 MHz ladder filter and a tunable LO. This worked with an active whip on the car.

Most people use base loaded vertical or Marconi top loaded antennas, Inverted L's or as with Frank, Inverted U antennas. My 187 kHz Beacon antenna was a base loaded conical diamond Monopole with a 20 ft diameter Top Hat.

Mike WU2D
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KM1H
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« Reply #19 on: February 23, 2012, 08:46:26 PM »

Im very happy with my TS-950SD performance below 500KHz which is where the 30dB built in BCB attenuator kicks in/out. The other xcvr is a TS-940 and Id be happy to have either one able to TX down there at any power level since a basically full quarter wave wont take much amplification from 100mw to be legal.

What started out as a 160' up and 325' out inverted L with elevated radials is presently 160' up with a pair of about 90' top hat wires which EZNEC says is a hair better in gain where I think I want it and not burning clouds. The argument remains: is that cloud warming RF capable of being useful for long haul ducting as is often the case on 160??

With 5 2 wire reversible 500-900' Beverages the directivity is excellent even though popular literature says different. In fact they still have enough directivity at the ~200KHz LF BCB that I can easily switch between EU/Mideast/N. Africa.
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Bill, KD0HG
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« Reply #20 on: February 24, 2012, 08:32:02 PM »

Homebrew only. Class C, Class E or resurrected old time military. Even parts kits that one has to assemble, test and debug. The last chance of Ham Radio to have something motivational to do with RF technology.

Bill
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