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Cal Amp 130016 downconverters

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Submitted by Sinager on Fri, 05/09/2008 - 16:55.

I noticed this auction on eBay 

http://tinyurl.com/6ejwcb

and got a couple... being the dollar so low these days I guess I can't go too wrong.

Apparently they can be easily widebanded simply bypassing/removing some filters:

http://www.rvhfg.org/articles/k0sm/basic%20mods.php

I've got equipment covering S band directly, but 30+ meters of coax from the roof  deterred me from experimenting.

Posting the link just in case anybody else is interested.

S

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hands on

Submitted by Sinager on Tue, 23/09/2008 - 18:16.

I started work on one unit: removed the copper "comb", bypassed the ceramic filter and cut traces to the 2.15 GHz one.

I haven't done the suggested mods on 2.4 GHz filter yet, as I wanted to check on the current frequency response. Using the 3rd harmonic from my generator I got this kind of output. Please disregard absolute values, as I don't know what the actual output might be.

Possibly due to the combined effect of LO noise (for sure, well visible on the spec.an.) and input filter, no signal was readable on the IF out for the enitre space segment.

130016_unmod.jpg

I tried posting this note on Sunday but can't see it.. I apologize if I messed with the forum

S

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I got the converters

Submitted by Sinager on Thu, 18/09/2008 - 13:18.

I got the converters yesterday and had the first peek inside. Reference crystal is indeed  at 8.8984 and therefore a 2278 LO right in the space segment.

Cunning plan: a 9,1797 MHz reference may allow for space segment (2200-2300) on the low side and video applications (2400-2600) on the high one.

Unfortunately that would require a special order crystal: all standard parts suppliers I could check on the web seem to jump from 9.00 to 10.00 Mhz.

I'll now check with "International Crystals" availability and price for small orders. This provider is mentioned in the WC0Y paper.

Other suggestions?

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mmm that was cunning in a

Submitted by Sinager on Thu, 18/09/2008 - 14:21.

mmm that was cunning in a "Blackadder" way .. I'd end up with unwanted images everywhere... I guess I'll have to settle for a single band

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S-Band Converters

Submitted by Nils on Fri, 05/09/2008 - 20:44.

Hi sinager, that are nice converters.
Is 2.1 to 2.6 GHz = 100 to 600 Mhz. ?
Are the converters frequency stabile?

Regards, Nils

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Converters

Submitted by pjm on Fri, 05/09/2008 - 22:02.

Hi Sinagar, thanks for the links, very interesting. I have a pair of these converters on the shelf that I've not done much with, my current plan is to move the LO down a bit to 2GHz and use the dielectric tuning method on one of the filters as per that article, I want good response over the Space to Earth band. I seem to recall the xtal oscillator in the PLL was pretty low in frequency, perhaps around 11MHz, cant remember off hand. Anyway, they are ok for SSB reception so short term stability is ok.

regards, pjm

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I just ordered them today:

Submitted by Sinager on Fri, 05/09/2008 - 22:44.

I just ordered them today: literature around suggests a LO at 2278 MHz when referenced to the original 8,89... MHz xtal. Coverage stated on the label therefore meaning  116-128 MHz IF for 2162-2150 (-) and 222-408 for 2500-2686 (+)

There's a current product from Cal Amp that may give some hints on specs and stability:  http://www.calamp.com/home/pro_mmds_131740.html

 More details on mods for units that sound very similar:

http://www.qsl.net/n9zia/31732/index.html
http://www.qsl.net/n9zia/wc0y/index.html

S

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