KJ7YY
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« on: March 17, 2012, 05:32:08 PM » |
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Anybody planning to homebrew a rig for the "new" 630 meter band? A qrp CW rig, tube type would be cool. Suggestions?
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W4OP
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« Reply #1 on: March 17, 2012, 05:44:16 PM » |
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It appears that Elecraft is going to be able to do a firmware upgrade to allows us K3 owners on the band with only a PA needed.
JUMA also has a 630M transverter.
Dale W4OP
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WB6BYU
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« Reply #2 on: March 17, 2012, 05:59:57 PM » |
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There are a number of designs for European 136kHz rigs that would give a good
starting point. While those with a good supply of tube parts can probably use
those, switching MOSFETs are an excellent choice at this low of a frequency.
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KB1WSY
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« Reply #3 on: March 18, 2012, 07:39:33 AM » |
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On the receiver end of things: not actually homebrew, but the 630m (472-479 kHz) band is squarely within the tuning range of the BC-453. Makes sense, since that WWII receiver was a navigational set for radio beacons. However I'm not sure it would be much use for hams trying out the new band. It would only be a single-conversion super, right? I just checked my own BC-453 and the 7-kHz spread of the new band is only about half of one turn of the little tuning knob. Still, when I get my "yet to be restored" BC-453 up and running, I look forward to seeing whether it is any use for copying the intrepid early users of the band.
73 from Martin, KB1WSY
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AC8JU
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« Reply #4 on: March 18, 2012, 04:06:12 PM » |
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With a power limit of 1 watt (or 5 watts depending on geography) an RF signal generator feeding a magnetic loop antenna tuned with a variable cap could be considered. My old Heathkit puts out about 20 MW and I haven't even looked at peaking it.
If it was kept under 100MW and the antenna and feedline were kept under ten feet would it be legal for experimentation under Part 15, pre-allocation? Tnx ~ M
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KE3WD
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« Reply #5 on: March 18, 2012, 04:57:22 PM » |
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20MW = 20 MegaWatts = 20 million Watts
I think your sig gen outputs 20mW or 20 milliWatts...
73
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WX7G
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« Reply #6 on: March 18, 2012, 05:02:33 PM » |
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The power limit will be 1 watt EIRP or 5 watts depending on your QTH. That means that an antenna having a radiation efficiency of 1% can be driven with 100 or 500 watts.
A 160 meter antenna tuned for 500 kHz will suffer a loss in efficiency to roughly 1/12. That means if your 160 meter antenna is 12% efficient (like my 30' base loaded vertical) all you need for 630 meters is a 100 or 500 watt amp.
I might design and build such an amp using cheap power supply FETs. The power supply for my ALS-600 will supply the power.
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« Last Edit: March 18, 2012, 05:07:03 PM by WX7G »
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VE3GRO
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« Reply #7 on: March 24, 2012, 09:06:14 PM » |
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DUST OFF YOUR 6L6s. Some of the wartime ARRL Handbooks have plans for carrier-current transmitters that operate on these frequencies. Can easily be adapted to feed into antennas.
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KE4YOG
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« Reply #8 on: March 24, 2012, 10:05:30 PM » |
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I am in the process of designing a 3 element yagi for this band. Now if people will chip in and help me buy the 1000 acres or so I am going to need it could be fun!
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AF6AU
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« Reply #9 on: March 30, 2012, 02:51:51 PM » |
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The January or February 1972 issue of Popular Electronics has a article of a 1 watt AM/CW transmitter for 160-190KHz, using a 12AU7, 12AT7 and a 6AQ5. It looks like it could be easily tweaked for this higher frequency.
My old copy is very poor and stained, I hope somebody has a better print than I do.
JML
AF6AU
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WB6BYU
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« Reply #10 on: March 30, 2012, 03:50:47 PM » |
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But that was 1 watt plate input power, for the license-free band.
Getting 1 watt ERP is much more difficult. It likely will require 50 - 200 watts
output from the transmitter because the antenna will be rather inefficient.
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KC2VDM
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« Reply #11 on: March 31, 2012, 04:42:09 AM » |
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I'd like to get on there sometime. LET THE HOMEBREW BEGIN!
-Alex
KC2VDM
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KG4NEL
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« Reply #12 on: April 01, 2012, 03:44:02 PM » |
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I am in the process of designing a 3 element yagi for this band. Now if people will chip in and help me buy the 1000 acres or so I am going to need it could be fun!
V8-powered rotator?  |
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KE4YOG
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« Reply #13 on: April 01, 2012, 08:34:44 PM » |
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I am in the process of designing a 3 element yagi for this band. Now if people will chip in and help me buy the 1000 acres or so I am going to need it could be fun!
V8-powered rotator? That is an idea. V8 rotator. Havent thought of that. Being a deer hunter I was think it could be antenna farm/deer hunting land. Might need to look into the gearing that will be needed to transfer the power! |
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KG4NEL
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« Reply #14 on: April 02, 2012, 12:00:29 AM » |
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I am in the process of designing a 3 element yagi for this band. Now if people will chip in and help me buy the 1000 acres or so I am going to need it could be fun!
V8-powered rotator? That is an idea. V8 rotator. Havent thought of that. Being a deer hunter I was think it could be antenna farm/deer hunting land. Might need to look into the gearing that will be needed to transfer the power! Gives new meaning to 4 on the floor... :p |
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