[TenTec] OT: Holiday SDR Project

[Carl Moreschi]

That's the only way the 1708 works for what is needed.  I have several 
of my users doing this.



Carl Moreschi N4PY
58 Hogwood Rd
Louisburg, NC 27549
www.n4py.com

On 11/9/2014 9:56 AM, george fritkin via TenTec wrote:
> To whomever reads  this......using the jumper on the MFJ 1708 is not a good idea
>
> George, W6GF
>
>
> On Saturday, November 8, 2014 11:19 PM, Rick - DJ0IP / NJ0IP<Rick at DJ0IP.de>  wrote:
>
>
>
> On the topic of antenna switches for multiple receivers, there are such
> devices available.
> One such device is the DA-4 from RF Systems.
> See:  http://www.universal-radio.com/catalog/preamps/0601.html
> I've used this before but only with multiple receivers.
> I don't know how well it behaves around RF.
>
> The Eagle and Omni VII both have a mod which interrupts the RX antenna line
> and routes it to the back panel.  You could use the line out to drive a
> switch and have the line in be one of the outputs of this device.
>
> You would have to copy this mod for use with the OM6, which would be very
> easy to do since there is a lot of space inside the OM6.
>
> Or, do like I did and simply build your own 3-dB splitter.  Mine is a in a
> tiny square box about 2.5"x2.5"x1".
>
> If you don't want to make the splitter yourself, they are available
> commercially, such as the one from Mini Circuits, which claims only 0.3 dB
> insertion loss (though this is only possible with a broadband amp (I
> thought), yet I don't see any mention of an amp).
> http://www.minicircuits.com/pdfs/ZFSC-2-6+.pdf
>
> In the case of the Eagle, it inserts AFTER the RX-GND (protection) relay, so
> it is safe to use "as is" for this purpose.  I would have to look back at
> the OM7 circuit diagram to see if it has the same type of protection relay.
>
> If you d-i-y, you would need to add the protection relay yourself, just
> before splitting the RX ant out.
> This type of solution enables both receivers to work at the same time,
> though usually with 3dB loss, which most of the time is not even noticeable.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Don
> Rasmussen via TenTec
> Sent: Sunday, November 09, 2014 7:04 AM
> To: tentec at contesting.com
> Subject: Re: [TenTec] OT: Holiday SDR Project
>
> Great info Carl - thanks.
> Sounds like Corsair 2 has the best option for passing the receive but that
> is not a CAT radio for N4PY software so yes, some external antenna switching
> would be needed as you suggest. I prefer a universal solution so maybe the
> MFJ or a DX Engineering RTR-1A and using the amp control line to activate
> it.
>
> I was never a big one for panadapters but figured with a $66 SDR receiver
> there might be a simple/inexpensive solution for that - any way I look at it
> seems to be a couple hundred dollars - hi...
>
> =====================================================================
>
> What radio are you using? Many radios have an easy way to share antennas. If
> that's not an easy solution then the MFJ1708 can do the job. See below.
> The solution to share antennas is to add an MFJ-1708 T/R switch.  This unit
> will automatically sense RF from the transmitter and then remove the
> panadapter radio from the receive antenna connection.  But the MFJ switch
> will also remove the transceiver from the transmit connection while in
> receive.  So the MFJ switch needs a very simple mod.  You must solder a 14
> gauge wire between the transmit and antenna SO-239 connections.  This will
> then make the switch operate properly for this use.  Additionally, you can
> wire the relay to energize from your radio's amp key line for faster and
> safer switching. Carl Moreschi N4PY
> 58 Hogwood Rd
> Louisburg, NC 27549 www.n4py.com
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