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Author Topic: 902 mhz???  (Read 15340 times)

Posts: 133

« Reply #15 on: January 28, 2012, 09:44:01 PM »

Can anyone comment on the 23cm band? Has anyone used repeaters on this band,and if so what kind of range is typical? Do the signals behave similiar to 902 mhz?

23 cm is more line-of-sight than 33 cm. I've never worked 23 cm band, but my friend Ed, KE6VRK, has, and he says 23 cm signals won't do some of the things a 33 cm signal can be made to do (his latest trick has been to point his 33 cm beam at aircraft passing overhead in order to bounce his signals off them to other hams on the ground---his "rent-free repeater"). He says 23 cm is more suitable for D-Star, if that's what you're running.

But as far as bands being off-limits... yeah, here in L.A. that's old news. Apparently the bandwidths of the military radars on 70 cm and all the ISM gadgetry in and around L.A. are so much wider or narrower than run-of-the-mill 5 khz ham deviation, that QRM isn't much of a problem... heaven only knows what kinds of devices they're using at UCLA and other hospitals, yet I've never received any QRM when driving by any hospitals with the Alinco monitoring 33 cm.

Re other manufacturers not taking the chance... Alinco is sort of like the Chrysler of ham radios... they are not afraid to introduce something new and different (even if it turns out to be a dud like the '34 Airflow or Alinco's 1st edition of the DR-MO6---what a piece of junk that radio was!). It won't be long before the team at Yaesu, Kenwood, or Icom put 2 and 2 together and hop on the 33 cm bandwagon once they've seen the Alinco's sales figures.

The lesson here is... never say never!  Roll Eyes
73, Marty

Posts: 1256

« Reply #16 on: February 02, 2012, 12:39:02 PM »

Thanks for the info,appreciate it.-Mike.

Posts: 1553

« Reply #17 on: March 04, 2012, 06:12:51 PM »

 heaven only knows what kinds of devices they're using at UCLA and other hospitals,
The lesson here is... never say never!  Roll Eyes
73, Marty

Locally, our guys moved the input freq of the main repeater to the very bottom of 902.  What was happening was that so much ISM Part 15 from the hospitals was getting into the input freq of the repeater and creating some very annoying popping noises that resembled a bunch of race horses' hooves on a track.  After delving into the band with a spectrum analyzer hooked directly to the repeater antenna, it was shown that the very bottom, close to 902, and the very top, close to 928 was the way to go.....very clean at the band edges.  The guys in the NORCAL group had a very similar experience, and suggested this to us.

Similarly, but yet a different matter, are the paging systems that are still used primarily by physicians, so again, hospital areas are a problem.  The pagers aren't Part 15, or in 902-928, but they're rock-crushers in power and blast out data (around 930 MHz?) with a vengeance. This will overload front ends of 902-928 radios and repeater receivers, so it's another frustration.  Good quality front end filters are the answer in this case.  

OK, a little League-bashing from a supporter and Life Member.....they have been way, way behind on this, wrt the 902 band plan.  It still includes significant chunks for ATV, which is all but dead, here at least.  Too, the 25 MHz offsets, not the 12 MHz offsets implied by the League plan, are what's needed as so many Motorolas, GEs, etc require this.  So.....the 902.XXX/927.XXX offsets are no accident, but still not a concept absorbed by the League for some reason.  BIG frustration there....WHAT are they doing??  

Anyway, just some thoughts.  Best of luck in your 33 cm endeavors.

Brad, K9MHZ
« Last Edit: March 06, 2012, 04:29:35 PM by K9MHZ » Logged

Posts: 133

« Reply #18 on: March 04, 2012, 09:32:21 PM »

As I write this, I just got done making the elements for a couple of 33cm loop yagis for Ed Lemus, KE6VRK, and myself.

I still have enough metal left over to build at least 6 more of these yagis, if anyone is interested.  Grin
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