Transverting up to 10GHz

Discussion about this major DATV Project. See also https://wiki.batc.tv/The_Portsdown_Transmitter
g0mgx
Posts: 19
Joined: Sat Dec 31, 2016 7:57 pm

Transverting up to 10GHz

Postby g0mgx » Wed Sep 13, 2017 3:50 pm

Hi All,

As briefly discussed at CAT17, I am wondering about using my Portsdown to drive a Kuhne 3cm transverter.

Has anyone done this?

Thinking about bandplans and other such goodies, a target frequency of 10,360 MHz would seem reasonable being right in the middle of the "digital modes" section. According to my ropey maths that means I need an input to my transverter at 136 MHz.

I'll do some experiments first with a signal generator and a spectrum analyser first to see how the transverter performs outside its target 144-146MHz IF, but I'm wondering:

  • Has anyone actually tried this?
  • Can we have custom RF target frequencies as a software option in the Portsdown so we can drive various transverters at odd frequencies?

Discussion welcome.

Mark
G0MGX

G8GKQ
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Re: Transverting up to 10GHz

Postby G8GKQ » Wed Sep 13, 2017 7:33 pm

Hi Mark

Given the level of activity on 10 GHz, I see no harm in operating closer to the Narrow Band Segment (10368). As long as the main signal does not overlay the 10368 - 10369 portion of the band I don't think anyone will get upset. I personally run 333KS on 10367 MHz, which would be an IF frequency of 143 MHz for you (it's actually an IF of 437 for me with my G3WDG transverter, but that's another story).

You can amend the frequency of the touchscreen presets from the Console Menu. Option 1 in the Advanced System Setup Menu lets you enter whatever you frequency you want. The button will be relabelled with the frequency entered.

I suggest you dive straight in and try it. The only thing that you need to watch for is getting the drive level correct so that shoulders do not get too high.

Dave

g8gtz
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Joined: Wed Apr 07, 2010 6:26 pm

Re: Transverting up to 10GHz

Postby g8gtz » Wed Sep 13, 2017 7:55 pm

Hi Mark,

I actually use a DB6NT Mk3 transverter with a 432 IF for NB which when driven by 437 DATV puts me on 10373MHz.

The transverter is very wide as the only frequency selective components are the pipe caps at 10 GHz and these seem to be several 10s of MHz wide and are there primarily to reduce the IF image. In fact mine was a 144 MHz IF unit in which I changed the crystal to get a 432 MHz IF.

As Dave says, band occupancy is not an issue and as long as you stay clear of the NB section 10368 - 10369.5 there shouldn't be a problem.

However, with everyone on different frequencies, the maths are a challenge when out /p so maybe we should adopt a DATV frequency and don't see why it shouldn't be 10360MHz. To save everyone doing the maths the numbers would be:

Tx
144 MHz IF transmit = 136 MHz
432 MHz IF transmit = 424 MHz

Rx
Serit tuner = as per Tx frequency
SUP2400 for 144 IF = 2264 Mhz
SUP2400 for 432 IF = 1976 MHz

Comments?
Noel - G8GTZ

g0mgx
Posts: 19
Joined: Sat Dec 31, 2016 7:57 pm

Re: Transverting up to 10GHz

Postby g0mgx » Thu Sep 14, 2017 4:24 am

Thanks for the pointers both,

I've already done the tests and as you suggest the transverter is wide open and works well with an IF input at 136Mhz.

I will report back once I've driven this with the Portsdown and post some images of the output spectra.

Mark
G0MGX

g0mgx
Posts: 19
Joined: Sat Dec 31, 2016 7:57 pm

Re: Transverting up to 10GHz

Postby g0mgx » Thu Sep 14, 2017 10:21 am

Here's three spectra with varying amounts of attenuation into the transverter; they all look the same just lower.

DSC_0031-Optimized.JPG
DSC_0031-Optimized.JPG (149.6 KiB) Viewed 363 times


I'm only seeing about -8dBM from the Portsdown at 136MHz, so thats not really enough to fully drive the transverter.

Will take me some time to convert this from something working on the bench to something I can take to a hilltop.

More projects!

Mark
G0MGX

G8GKQ
Site Admin
Posts: 561
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Re: Transverting up to 10GHz

Postby G8GKQ » Thu Sep 14, 2017 11:15 am

Hi Mark

Have you got some attenuation after the Portsdown? You should be getting nearer +10 dBm out of it at 136 MHz.

Dave

g0mgx
Posts: 19
Joined: Sat Dec 31, 2016 7:57 pm

Re: Transverting up to 10GHz

Postby g0mgx » Thu Sep 14, 2017 12:08 pm

Interesting, my Rigol says +10dBm

Untitled.png
Untitled.png (29.45 KiB) Viewed 348 times


Falling foul of my own stupidity somewhere along the lines; I'm not used to such wideband signals and I suspect my resolution bandwidth is playing tricks on me.

Mark
G0MGX


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