[222mhz] ACSB

[Dr. Gerald N. Johnson]

On Tue, 2007-11-06 at 23:45 -0600, cboone at earthlink.net wrote:
> ACSSB hasn't changed since the early days...the "pilot" tone is 10db down from max carrier out (It does do 0dbC at initial keyup then drops to -10dbC after 10-100ms iirc; by that time, the rcvr should have synced onto the pilot and thus the lower level can be used; much like the inband 3825 Hz pilot tone -used for E&M signaling- on SSB multiplex for analog FM microwave) and is 3.100 kHz from lowest end of the channel. The pilot is also low level FMed for PL/DPL use. 
> 
> As to getting them up on the 222-225 MHz range, it will be rough. The CPU mask is probably written to prevent out of range programming. You would have to come up with a new PLL control system or a new CPU with a new mask that allows programming outside the 220-222.0 range. Shame that it cant if SEA confirms that.
> 
> ACSSB did not ever take off on 220 (or even VHF HiBand for that matter) and NOW very narrow band FM (2.5 kHz deviation) is being used there....so much for spectrum efficiency (and to think poor UPS got screwed in the end....ahhhhhh) I have seen LOTS of SEA 220 systems at several tower sites turned off or if they are turned on, noone is using them....they just sit there, occasionally burping for "home" channel purpose and IDs..What a waste.....Funny how Motorola got into it when FM was authorized...they do sell a CDM mobile on 220-222 and sell rptrs made by Spectrum Engineering out of Australia (They don't even sell their own repeater...does that tell you something?). One of my company UHF repeaters grabbed on to the 1.5 in Heliax used by a 220 system. I have tried to find the 220 antenna they took down (20ft fiberglass)....but the other 220 ant w/feedline is still on the tower (HMMM Sounds like a ripe site for a 220 rptr)
> 
> The gear IS good for parts (The combiner/duplexers are a little rough to make work for single channel 1.6MHz split rptrs according to Sinclabs..it can be done but not worth the effort); The PA will be great for an all mode xvtr to 220 from another band; so would the front end but the LO and IF will be screwy....but as to making them actually work on 222-225, thats gonna be rough....but I would be interested if there IS a way..Midland also sold some "Linear Modulation" radios for 220 (May have been ACSSB or possibly some form of QPSK...not sure) and I think they can be programmed for simplex above 222....but I have never confirmed that rumor (Midland has usually been good about allow their gear to go into amateur bands...once you dig the info out of an engineer at their factory ;)
> 
> Having real SSB repeaters on 222-225 would really be nice.....think of the range coverage, etc.....would beat any FM system....but again, if the radios cannot be reprogrammed, we are just SOL..funny, the HAMS would make more use out of it then the commercial guys ever did!
> 
> Chris
> WB5ITT
> 224.5 / 224.8 (and loss two control / link channels in 220 range to ACSSB)

Since we hams know how to tune and how to listen to noise and don't so
much need the perfect tuning and squelch of the pilot tone working to
make SSB sound like WIDE BAND FM, we probably can get along without the
ACSB parts and just use some of the pieces for ordinary SSB. And SSB
repeaters have been built for nearly as long as FM repeaters, and many
flown on Oscars.

As we go narrower FM deviations, we might as well go raw SSB though in
commercial circles SSB would give way too much range. The narrowness off
deviation and channel gives shorter range but gives more channels to be
used and allows closer reuse of a frequency and though the narrow FM
works poorly compared to the wide FM did when I was 40 years younger
(and I've been on 2m FM since 1959, first with a club station and then
with my own radio in 1961) the added channels make it sell. It looses
range and quieting (and so recovered S/N). Commercial interests are not
ham interests and going narrow is far less a benefit on ham bands, but
its here as a spill out from commercial practice.

With 15 KHz deviation we used to work simplex mobile to mobile at
distances now worked only with repeaters at least a few hundred feet up.

Don't Sinclair cavities have series capacitor adjustments on the links
or other ways of adjusting the link coupling? If they do or that can be
added the splits can be easily changed because the split in a notch
cavity comes from the leakage reactance of imperfect link coupling to
the resonator. And gives the notch/pass effect. Sometimes a shunt
variable at the link works too, depends on the size of the link.

73, Jerry, K0CQ