[hpsdr] Possible 5 band VHF transverter?

Thu Mar 14 17:18:32 PDT 2013

I agree Helmut this approach will not be as good as a well designed 3rd 
overtone oscillator in the VHF region, however it will be acceptable. 
This transverter is a multiband device that will be much cheaper and 
smaller than the traditional topologies. It is not designed for a 
contest station on 2m on a hill top.

The MAX2870 is not the device that I have in mind but the performance is 
only a little better.

A low phase noise super linear transverter is a different exercise and 
one that I am really interested in tackling as well, but later.

Despite that when coupled with Hermes it will be much better than the 
typical VHF radio and rather better than the run of the mill transverter 
designs that are out there. Not all Xtal oscillators are made equal.

However at this stage until I have done more testing and looked at the 
reality of the spurs from the device and therefore the filter 
requirements I am not prepared to share a block diagram.... yet. When I 
have the building blocks in place and have tested them - and I have some 
performance figures I will of course be prepared to share.

Can I just ask again (as I do not have a Hermes yet) is high side 
injection feasible with PowerSDR? On 70 MHz I would like to use high 
side injection. My LO frequency range with the proposed device is 85 - 
2700 MHz.

I am chiefly interested in weak signal modes such as EME and close in 
phase noise is not that important to me, I don't have any truly strong 
signals above 50 MHz locally. I do have some stations who are quite 
strong and clearly have their own phase noise issues :) Improving things 
my end won't make any difference with those guys; fortunately they go to 
bed early.

If any one has any ideas for a multiband transverter that can achieve 
-146 dBc @ 10 kHz I'd love to hear your ideas.

So to summarise, my design as it stands will degrade Hermes by up to 20 
dB/Hz @ 10 kHz offsets above 432 MHz however it will be a Hermes sized 
box that will do at least 5 bands. When I know that it will work I will 
publish a block diagram and ultimately construction details, pcbs etc.

For the best strong signal handling mono band transverters with LO based 
upon a Xtal still wins out from what I have seen so far, I just fancied 
doing something a bit different.

Whatever I do its got to be better than the awful Icom IC910 that we 
have at our radio club!

73

Conrad G0RUZ

> Hi Conrad and Phil,
>
> I’m afraid the even the MAX2870 is no good choice. A 5 band application 4m,
> 2m, 70 cm, 23 cm and 13 cm, requires LO-frequencies between 20 and 2400 MHz
> assuming an IF covered by standard HPSDR. MAX 2870 datasheet shows phase
> noise between -130 dBc/Hz and -100 dBc/Hz@ 10 kHz offset for these
> frequencies. This is at least 20 dB worse than the traditional design using
> a xtal-oscillator an multipliers and will reduce the TRV performance
> dramatically.
>
> 73, Helmut, DC6NY
>
> -----Ursprüngliche Nachricht-----
> Von: hpsdr-bounces at lists.openhpsdr.org
> [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Phil Harman
> Gesendet: Donnerstag, 14. März 2013 11:55
> An: Conrad Farlow; hpsdr at openhpsdr.org
> Betreff: Re: [hpsdr] Possible 5 band VHF transverter?
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Conrad,
>
> You may like to consider the MAX2870 integrated VCO/Synth.  I've been
> evaluating one for the Cyclops Spectrum Analyser project and the phase noise
>
> is quite good in comparison to other devices.
>
> 73 Phil....VK6APH
>
>
>
> -----Original Message-----
> From: Conrad Farlow
> Sent: Thursday, March 14, 2013 11:34 AM
> To: hpsdr at openhpsdr.org
> Subject: Re: [hpsdr] Possible 5 band VHF transverter?
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> I am working on a multiband transverter for Hermes, its early days but I
> have narrowed down my choices of Silicon. It will be possible to lock to
> either the 122.88 MHz Hermes oscillator or a 10 MHz ext source . It's a
> synth but the phase noise is very reasonable for an integrated VCO/Synth
> based design .
>
> I had forgot about 220 MHz but there is no reason why it could not be
> accommodated.
>
> I hope that the transverter will work up to 13cms and down to 4M.
>
> TX Output will be of the order of 23 dBm with some 10W amplifiers to
> come later. This seems to be a sensible output power given the drive
> requirements of a modern LDMOS devices.
>
> I still have a LOT to sort out but so far I am very encouraged that I
> can make this happen and that the transverter will be better than older
> designs and will use modern devices that should have a long shelf life.
>
> I will post some performance figures as I develop the boards, I expect
> that it will take me 6 months or so to complete with my current workload.
>
> 73
>
> Conrad G0RUZ
>
>
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> This chip has been around for a couple of years, but this board might make
>> a nice transverter for Hermes.  6 dBm out.  Too bad it won't reach down to
>> 2M and 220.
>>
>> http://myriadrf.org/
>>
>> The Kickstarter Blade project would be more in line with this board, but
>> only has a 12 bit receiver.
>>
>> N0UU
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