At 02:38 PM 5/17/2010, tosca005@umn.edu wrote:
On May 16 2010, Sebastian wrote:
Perhaps others such as DEMI, will see this as an opportunity and come up with alternatives?
Well, keep in mind that DEMI's strength is in transverters, and what is hard to obtain for satellite operation from most common-place existing equipment is a full-duplex transceiver. I don't think that DEMI is likely to start building transceivers, but if you had a true full-duplex transceiver, they would have transverters available to upgrade the radio to the satellite bands needed.
Completely doable with current xvtrs. Tell them what frequencies you want.
Here's a thought: buy two SoftRocks for a lot less than the price of the Flex 5000 -- one would be the v6.3Rx/Tx and the other could be the V9 Rx only. This would net you two independent receivers and one transmitter, and with clever wiring, selection of VHF & up transverters, and maybe a little bit of software development, you could turn that into a software-defined radio that would be capable of full-duplex cross-band operation. (The V9 Rx would be the primary receiver, the receiver in the V6.3Rx/Tx would be "spare" or "extra" or even ignored.) You'd need to configure the transverters with "split IF"
Huh? Why? Put a xvtr for the uplink band on the Tx and another xvtr for the downlink for the Rx.
, and use two coaxial relays to route the 28 MHz SoftRock IF Rx and Tx separately to the correct receive and transmit transverters.
I thought you had two separate Softrocks, so why the relays?
A bit of innovation/homebrewing would be needed for convenient band-switching, since you would need to switch two different transverters into the correct "position" depending on the mode: V/U vs. U/V vs. V/S vs. U/S vs. L/S vs. L/U vs. whatever other modes you wanted to support. But 4 transverters (145, 435, 1269, and 2400 MHz) would give you lots of satellite modes.
four xvtrs would give you every conceivable combination of up and down link: V/U, U/V, V/L*, L/V, V/S, S/V, U/L*, L/U, U/S, S/U, L/S, S/L* * These modes are not allowed for Amateur Radio space-coms.
If each xvtr was configured for separate Rx and Tx antenna and IF connections the configuration tree would be simpler. I count nine configurations (excluding HF bands). If eighteen coax relays seem a bit much, make a coax patch panel and use coax jumpers to configure for the mode you want.
Oh, don't forget there are some birds with HF links and the SoftRock can do HF natively too...
If only I had the time to work on such a thing...
Ideally, the transverters would be dual frequency, so that you could tune to 432 terrestrial or 435 satellite; 1269 satellite or 1296 terrestrial; and 2304 terrestrial or 2400 satellite.
With the newest xvtrs using PLL in place of xtal oscillators; this is a dc switch to shift LO's. I am installing PLL's into my 1296 and 3400 DEMI xvtrs.
Newer DEMI transverters with the synthesized LO board can be configured that way, at least on the higher bands. Then you'd have not only a kick-@$$ satellite system, but also an outstanding weak-signal terrestrial system.
DEMI is planning for PLL from VHF up (when they can get to it). PLL available now 1296 and up.
Unfortunately, DEMI is once again revamping their lineup of products. Of course, this is good for us who want the latest and best, but bad for us who want something right NOW. Prices and specs are a little bit harder to obtain from DEMI right now, but I expect that the wait will be worth it.
Prices are announced on the webpage. Some of the xvtrs are shipping in June (I have 144/28 ordered). They are shipping assembled units first, then will offer kits later in the summer.
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-600w, 432-100w, 1296-60w, 3400-fall 2010 DUBUS Magazine USA Rep dubususa@hotmail.com ======================================