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A question about two radio operation and dopplercorrection

I'm in the market for a new or used satellite radio so I can get back into the swing of things and Ive explored several avenues including all the popular sat only or sat/HF combination rigs. I have nothing now really now so i'd like Hf capability as well. The money I was expecting for my new radio venture hasn't appeared as quickly as I would have liked so I've been researching a lot of ways to "skin the proverbial cat" so to speak. One of the first approaches I thought of was a two radio setup to allow full duplex operation with SatPc32. My plan was to accquire a couple of Yaesu FT-857's or 897's for this purpose.Unfortunately I've been told by several people and Erich also confirmed for me, on his FT-817 at least, that the radio will not allow frequency changes while transmitting. I know that these rigs are not true sat radio's per se but this seems odd to me. At any rate, in my mind, this would seriously affect the systems ability to carry out true doppler correction. Am I correct in this assumption or would it be sufficient for the tracking program to only update the TX in between transmissions?
 The only reason I've considered this approach is that it might be easier for me to buy one rig now and another  a few months from now. I have a 2m FM which would allow me full duplex operation on the FM birds but later down the line after purchase of a second rig I would be able to go to the linear sats.
 I'm looking at true sat radios but this issue has been somewhat gnawing at me and I'd like to rule out the dual radio approach before continuing further in my deliberations.
Thanks and 73,
Michael, W4HIJ
AMSAT # 36017
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author.
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