DDS VFOs

[N2RJ]

Anyone here played around with a DDS VFO?

I was thinking of getting the DDS-60 from AmQRP to possibly use in a SDR or even a conventional transceiver design.

[kc2orw]

Never played with one but have seen it and had thought about getting one. If you go for it do tell all of us about your experiences with it...

[N8YX]

I built one of their kits about a year and a half ago...another sits
unassembled, waiting for me to finish it.

Plans are to tie the unit to a BASIC Stamp or a PIC. They'll be tuned
by means of an optical encoder and I'm going to use the completed
assembly as part of a replacement 'PTO' for my Drake 7-line equipment.

Unlike the Misty Hollow units, my version will be internal.

It'll mimic the RV75 in terms of functionality (i.e., 10hz tuning steps,
RIT and so forth).

The NJQRP design looks to be fairly clean and free of hash. I would
recommend them to anyone who is looking to build a DDS VFO.

[N2RJ]

Nice.

So what do you plan to do with your VFO? Use it in a receiver/transmitter or use it as a signal generator?

http://groups.yahoo.com/group/dds-vfo/?yguid=270323167

There is a DDS VCO Yahoo group. It has a lot of insight.

[N8YX]

Nice.

So what do you plan to do with your VFO? Use it in a receiver/transmitter or use it as a signal generator?

I'm going to build mine into a small aluminum box...which will serve as
a drop-in replacement for the TR7/R7's PTOs.

The stock PTOs drift a bit, even with the correct temperature-compensation
components installed. (When these rigs and their subassemblies were
manufactured, the PTO components were selected by hand...based on the
amount and direction of drift over a given time period.)

If you can find the elusive RV75 (a Drake synthesized VFO), you will
spend upwards of a kilobuck for a nice one.

There's got to be a better way...

What I'll ultimately end up with will replace the stock PTO assembly - will
not drift - and can be computer-controlled to boot. The hardware is
laid out at the moment and I'm currently writing the up/down tuning
code (in PBASIC).

Most STAMPs have a 20MHz clock and they radiate a horrific spur at or
near that frequency. Parallax's latest variant has a 32MHz clock and
can communicate serially at 19.2K...this should work well for my
intended application, as it moves the offending spur completely out
of the HF region.

[N2RJ]

Cool.

That doesn't sound like a bad idea. Clock it with a GPS clock source and you have a frequency reference!

[N2RJ]

http://groups.yahoo.com/group/dds-vfo/?yguid=270323167

There is a DDS VCO Yahoo group. It has a lot of insight.

Not bad. I so wanted to get the I/Q pro but KangaUS is sailing right now and not taking orders. :(

[KA5PIU]

Hello.

I have an FT-107 that somebody replaced the memory unit with a DDS VFO in.
This works great, as I can tune 12 MHz on each side of the band. :)
The internal VFO can only do .5 MHz.
True, one quickly goes past the passband of the receiver, but I can tune from 100 KHz to 42 MHz, and have hundreds of memory positions in place of 12.
This mod was done without any changes to the radio proper, the memory unit was removed and this was put in its place.
I like it very much over the original Yaesu memory unit, it is RF quiet also, where the Yaesu unit is not.
This is based on the Analog Devices DDS chip.
Replacing the chip with an updated unit will give DC to 31 MHz.
That would put the radio at 66 MHz in the high ten meter position. :)
The VFO in the radio is intended to do 5 to 5.5 MHz, not DC to 31 MHz.
But, 1.5 MHz is, within limitations, fine.