my 500kc PTO in progress

[K5UOS]

Well, this isn't the fancy rack and pinion drive I wanted, but I might be able to make this work. Something to do with all these ferrite slugs I picked ujp at Dayton!

EricAttachment 98175Attachment 98176

Hi Eric,

What type of mixer will you use in the DC receiver? What kind of audio amplification?

DOn K5UOS

[KB7NRN]

My question about this new band is, how usefull is 7khz gonna be. I mean, you can have what, maybe 2 or 3 CW QSO's goin on at one time?
With PSK you could have a bit more...maybe 6-9 QSO's.

Eric, I don't mean to rain on your parade, it just seems like a lot of work of so little gain. I know there's the fun of experimenting with something different and that has it's merits but I'm just not too worked up about 7khz. Now if we had a 100khz slice of bandwidth then you could really do something.

Well I guess it's the first step to more bandwidth so I sould be thankful.

John

[AF6LJ]

My question about this new band is, how usefull is 7khz gonna be. I mean, you can have what, maybe 2 or 3 CW QSO's goin on at one time?
With PSK you could have a bit more...maybe 6-9 QSO's.

Eric, I don't mean to rain on your parade, it just seems like a lot of work of so little gain. I know there's the fun of experimenting with something different and that has it's merits but I'm just not too worked up about 7khz. Now if we had a 100khz slice of bandwidth then you could really do something.

Well I guess it's the first step to more bandwidth so I sould be thankful.

John

From what I read many are using digital modes on that band.

[K1AO]

You might want to try a 455KHz PTO from Fair Radio Sales. I have modified many over the years. They would be easy to get to 500 KHz. They are now at $21.00 but, when one considers the electro-mechanical problem is solved, which is the most significant problem with PTOs (ask Ten Tec and Drake) it really is worthwhile. I have modified one to output 5-5.5 MHz by modifying the coil. One word of caution: Any kind of excessive force on the coil terminals can result in a terminal breaking out of the molded coil form. Not a problem when one is aware of it. Worth a try:

[W4OP]

My question about this new band is, how usefull is 7khz gonna be. I mean, you can have what, maybe 2 or 3 CW QSO's goin on at one time?
With PSK you could have a bit more...maybe 6-9 QSO's.

Eric, I don't mean to rain on your parade, it just seems like a lot of work of so little gain. I know there's the fun of experimenting with something different and that has it's merits but I'm just not too worked up about 7khz. Now if we had a 100khz slice of bandwidth then you could really do something.

Well I guess it's the first step to more bandwidth so I sould be thankful.

John

In QRSS modes, you can run stations spaced as little as 10Hz apart- or narrower. That allows for hundreds of stations. Here's a link to some of the 13.555MHz beacons running in QRSS. The vertical scale on the right is in Hz:
http://www.parelectronics.com/images/ARGO00000.jpg

[KL7AJ]

Hi John:

I'm part of the 500KC experimental group that led up to the granting of the actual license. It's quite amazing what folks are doing there...it's a great proving ground for low-noise reception techniques....anyone who's really interested in advancing the radio art is going to be interested in this band. Sure, it's not a high data rate thing..but for pulling signals out of the mud, it's a great test of one's technical prowess.....it's what ham radio is really about.

My particular interest in this band is for physics research....I go into this in great detail in my upcoming ARRL book, Radio Science for the Radio Amateur. 500 kc holds great promise for the detection of high energy particles (magnetic monopoles, Higgs Bosons, etc.) by looking at their radio signatures.

Stay tuned!

Eric

[KL7AJ]

Hi Eric,

What type of mixer will you use in the DC receiver? What kind of audio amplification?

DOn K5UOS

HI Don:

I have a nice collection of Minicircuits DBM modules. I'm going to be using a pretty strong local oscillator....+27 dbm, which will give me lots of dynamic range. For the audio section, I'm going to use three stages of OP-37 op amps...each stage using Salen-Key low-pass filtering....I like running multiple stages at relatively low gain...this allows me to build very sharp cutoff filters.

My next revision is going to make this an !/Q receiver, so I can do coherent detection .

Eric

[KL7AJ]

Actually I have a bunch of Blaupunkt Volkswagen AM radios that have great PTOs. And they are indeed well built. I just wanted the challenge of rolling my own...or perhaps numerous units......I'm sort of a masochist.

Eric

[WA7PRC]

You might try a small tuned loop for reception. It's possible to get a real sharp null with one of these....unless of course, the noise is coming from everywhere.

Eric

I've used the "box loop" antenna to DX on the MW BC band with great success. With an air variable capacitor and light coupling to the pickup loop, they have VERY sharp tuning as well. A vernier drive on the capacitor (or a smaller variable w/ low loss padding) is a good idea.

[KL7AJ]

iT'S DONE!

The electronics is ugly but the waveform is beautiful.