[hpsdr] A few questions

Mon Feb 18 04:21:18 PST 2013

Hi Conrad,

It's here:

http://openhpsdr.org/wiki/index.php?title=File:HPSDR_SSB_Phase_Noise.jpg

The plot is for Mercury but since we use exactly the same  hardware and FPGA 
code for Hermes I would expect it to be similar.

This is with the 122.88MHz VCXO phase locked to the on board 10MHz TCXO. 
The actual open loop close in phase noise of the Crystek VCXO is about 12dB 
worse - you will find the graph on their web page.

73 Phil....VK6APH

73 Phil...VK6APH

-----Original Message----- 
From: Conrad Farlow
Sent: Monday, February 18, 2013 8:11 PM
To: hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] A few questions

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

Where can I find a plot of the Hermes 122.88 MHz clock phase noise.

__________________________________________________
73

Conrad G0RUZ IO93FR
__________________________________________________
On 18/02/2013 08:10, Helmut, DC6NY wrote:
> 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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>>>
>>>

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