[hpsdr] Proposal for a 'low-end' RX/TX board for HPSDR

Tue Jul 25 13:28:42 PDT 2006

The P/P circuit appears to offer the highest claimed IP3.  Makhinson claimed output IP3 of 48dBm with 8dB gain and 2dB noise figure. Of course there is no guarantee a subsitution of the MRF586 will give the same result. Not sure if the TT1-1 output transformer has a cntr tap, but if so would be ideal for balanced input to the QSD/QSE. Possibly though not so conveient for a diplexer.
  ----- Original Message ----- 
  From: Ray Anderson 
  To: hpsdr at hpsdr.org 
  Sent: Monday, July 24, 2006 9:43 PM
  Subject: Re: [hpsdr] Proposal for a 'low-end' RX/TX board for HPSDR

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    Can anyone comment on what attributes the Makhinson (N6NWP) circuit (which is essentially a pair of Norton amps in push-pull) brings to the table that would make it preferable over the Norton amp in this application.

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  ----- Original Message ----- 
  From: Ray Anderson 
  To: hpsdr at hpsdr.org 
  Sent: Monday, July 24, 2006 9:43 PM
  Subject: Re: [hpsdr] Proposal for a 'low-end' RX/TX board for HPSDR

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

------------------------------------------------------------------------------

    Can anyone comment on what attributes the Makhinson (N6NWP) circuit (which is essentially a pair of Norton amps in push-pull) brings to the table that would make it preferable over the Norton amp in this application.

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>> I can see the argument for the front end LNA at 10 meters (or maybe even

>> 15 meters), but on the bands below that I think it may actually be a

>> liability unless you have an extraordinarily high IP3 for the preamp.

>> While this can be done it comes at the expense of quite a  bit of DC

>> current. This may not be a big deal but is something to be considered.

>Typicaly the LNA will take 60-80mA. Compared to what will disappear on tx

>it pretty insignificant. One advantage of some amplification will be to 

>lift rx noise floor compared to the spurs and sprogs from the LO and DIG 

>inside the enclosure!

>Ulrich suggested I think the BFG591 as a SMD alternative to the 2N5109 for

>mixers and amp. Maybe the part would go well either in a Norton

>configuration or the Mahkinson (N6NWP) MRF586 push pull pre-amp.

>Shel CT1IZU

Shel-

Good comments. Upon further consideration I tend to agree with you. 

The performance of a QSD can also be improved by including a diplexer between the BPF and the QSD to properly terminate the QSD input out of band. By utilizing the preamp the noise figure at higher frequencies is improved and the QSD also sees a constant termination impedance across a wide band since the amp exhibits 50 ohm input and output Z.

I've recently placed a schematic of a typical Norton amp on the Phoenix Wiki page. The schematic shows feedback turn s ratios set up for about 9.5 dB gain. Can anyone comment on what attributes the Makhinson (N6NWP) circuit (which is essentially a pair of Norton amps in push-pull) brings to the table that would make it preferable over the Norton amp in this application.

Does anyone have some target figures regarding performance that we should aspire to obtain? I think an IP3 of +40dBm with a dynamic range of at least 100 dB and a noise floor in the vicinity of -130 to -140 dbm are in the ballpark for state-of-the-art HF front ends these days.

I'm currently evaluating various options as far as preamps, QSD circuits, filtering etc. are concerned. If anyone has any favorite implementations that may be appropriate to Phoenix I'd like to see them during this evaluation phase.

73,   Ray   WB6TPU

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  ----- Original Message ----- 
  From: Ray Anderson 
  To: hpsdr at hpsdr.org 
  Sent: Monday, July 24, 2006 9:43 PM
  Subject: Re: [hpsdr] Proposal for a 'low-end' RX/TX board for HPSDR

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

------------------------------------------------------------------------------

    Can anyone comment on what attributes the Makhinson (N6NWP) circuit (which is essentially a pair of Norton amps in push-pull) brings to the table that would make it preferable over the Norton amp in this application.

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