[hpsdr] A few questions

[Helmut, DC6NY]

Hi Conrad, hi Phil,


I‘m successfully operating a 2m homebrew transverter using a +13dBm
Mini-Circuits ADE-25 mixer for rx/tx path, a 3-pole Temwell helical BPF and
some MMICs with Hermes but also with Mercury/Penelope/Metis. I prefer Hermes
due to minimal spurs on 10m IF.

As Phil mentioned low  phase noise of the transverter LO is most important
for the total performance. It’s a really good idea to use the 122.88 Mc also
as LO for the transverter.  If there is interest enough it should be no big
deal to design a PCB.

73, Helmut, DC6NY



-----Ursprüngliche Nachricht-----
Von: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Conrad Farlow
Gesendet: Montag, 18. Februar 2013 04:02
An: phil at pharman.org
Cc: hpsdr at lists.openhpsdr.org
Betreff: Re: [hpsdr] A few questions

***** High Performance Software Defined Radio Discussion List *****

Hi Phil well if no-one is designing transverters then some one should 
be! I suggest that we start the discussions by setting some performance 
goals, the last thing that we want to do is compromise the excellent 
receiver by limiting dynamic range due to excessive gain or choosing 
devices that don't cut the mustard.

Your comment on the LO is very interesting, using a 21.12 IF will still 
allow the use of sensible and achievable filters at 144 MHz. I rather 
fancy using active mixers for all transverters these days although I 
haven't really examined everything that is available yet. Transverters 
for bands above 70cms should probably use a locked synth LO as these are 
capable of excellent performance these days. I presume that it is 
relatively easy to tap off a small amount the 122.88 MHz clock? Active 
mixers only need small amounts of LO drive (-5dBm)  and offer good RF-LO 
and IF-LO isolation and don't need terminating with fancy diplxers which 
are the compelling reasons for using them.

Interesting times ahead.

__________________________________________________

73

Conrad G0RUZ IO93FR


On 18/02/2013 01:58, Phil Harman wrote:
> Hi Conrad,
>
>
> Welcome to the group. As far as I'm aware no one is developing
> transverters for use with Hermes. However, existing transverters are
> successfully being used with Hermes via the transverter port.
>
> In order to use undersampling with Hermes you would need to remove the LPF
> at the front end and the LPF following the pre-amp.  I've used
> undersampling to test receive on 2m, it works but needs a good preamp to
> be make an effective receiver.
>
> There are some spectrum analyser images of the output of Penny on the
> Wiki. I would expect Hermes to be similar. The 14 bit DAC will provide a
> limit to the performance of the transmitter.
>
> I've use the output from Penny as the RF source for a 2m Chirp beacon. I
> did use a BPF in order to attenuate the 122.88MHz clock but apart from
> that the source is very clean.
>
> I've also used the 122.88MHz clock as the LO for a 2m Rx converter - since
> it is very low phase noise ( <-130dB/Hz at 200Hz) and can be phase locked
> to an external 10MHz reference the performance is excellent.
>
> Please let they group know if you intend to design transverters since I
> would expect there will be considerable interest.
>
> 73 Phil...VK6APH
>
>
>
>
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hello all, firstly let me begin by apologising to the group if any of
>> this information is available by reading hpsdr list archives, if they
>> exist please point me to them.
>>
>> I am really only interested in 6m and above and so will require some
>> transverters, I am seriously considering designing some transverters
>> specifically designed to be used with Hermes. If anyone is already
>> working on this I would like to hear about it.
>>
>> My intention is to purchase an Apache radio, I haven't decided whether
>> to buy a ANAN-10 or their version of a Hermes yet. I have a high
>> linearity 30W PA that I could use as a driver for 6m.
>>
>> Anyway a few questions.
>>
>> 1. Has anyone successfully tried to undersampling for 70 MHz and 144 MHz
>> 2. Are there any plots of the TX output from Hermes - specifically TX
>> spurs - do I need  a BPF in the upconversion path of any transverters?
>>
>> --
>> __________________________________________________
>>
>> 73
>>
>> Conrad G0RUZ IO93FR
>> __________________________________________________
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>>
>>
>

-- 

__________________________________________________

73

Conrad G0RUZ IO93FR


G0RUZ webpages

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