Thursday, May 11, 2017

LEARNING the ART of LEVERAGING DUAL RECEIVE

















While most amateur transceivers support dual VFO's (A & B), only the top-tier radios support dual-receive (sometimes called Dual-Watch). Additionally, only the top-end of the top-tier radios provide the capability of dual-receive on different bands. The Kenwood TS-950SDX, Ten Tec Orion II,
Elecraft K3 and Yaesu FT-1000mp Mk-V & FTDX-5000mp are major players in the top-end.


I personally chose a fully-filtered Yaesu FT-1000mp for my dual-receive efforts.

The Secondary (or "sub") receiver is easily invoked by way of a Blue [DUAL] button perfectly located to the right
of the tuning knob.

Using the "`" key (top-left on the keyboard under the ESC key) in the N1MM+ logging software makes it easy to enable and disable the SUB receiver.




A caveat of dual-receive is that the VFO B receiver section (sometimes called the SUB receiver) is usually not as well filtered as the Main RX.

With the FT-1000mp, the 2nd receiver
is only dual conversion; whereas the
Main RX is a triple conversion deign.

Then again, the SUB-Rx is less
prone to signal "images".

While both receivers have independent AGC systems, the Shift/Width/Notch
and eDSP circuits are functional
ONLY with the Main RX.



Originally when I decided to relegate the FT-1000mp to main radio duty, I retired the
JPS NIR-12 and MFJ 752-C outboard DSP/FILTER units.
Now that I have brought dual-receive (SO2V) into WQ6X contest activities, these outboard audio conditioners have been given renewed purpose.

These units are now cascaded to process the Sub-RX audio (for VFO-B) effectively providing DSP audio processing for BOTH sides of my head.

After considerable operating time,
you will get a proper feel for what kind
of outboard DSP filtering is right for you.

Sometimes you WANT a more wide-open sub-receiver in order to look for other stations.

Then when you find one, if needed you can SWAP VFO's to actually work the station and then
Swap them back.  If you are running SO2-V in N1MM+, you don't need to swap VFO's; pressing
keys from data entry window "B", puts the radio in SPLIT mode before making the transmission
and then returns the radio to "normal" operation - a very CLEVER way of doing things.



The 1000mp is equipped with AF Gain controls for BOTH the MAIN/SUB receivers allowing me to customize the audio balance between both ears.

Additionally, thanks to the AF-REV button on the 1000mp, I am able to swap VFO A / B audio between left and right ears.

As you can see, the transceiver's menu system allows me to declare how the sound is ACTUALLY split up between the Left/Right channel of the headphones. 

I prefer to use the Stereo-1 setting which splits the audio between left and right ears, but with only 80% isolation; not 100%, as experienced with the Stereo-2 setting.




Because the FT-1000mp was designed specifically for dual-receive, putting the 752-C and NIR-12 in the right channel audio line to process the SUB-Rx is not a difficult undertaking.

It was only recently (during the 7QP/NEQP contest weekend) that I first tested this configuration using RCA-style audio patch cords.

[CLICK HERE] to read more about that setup.

For a more permanent setting I will make a set of custom audio cables directing the output to yet another device - a Radio Shack stereo equalizer.

The equalizer's 10 settings per channel will provide final "shaping" of the frequency response for each ear individually.



Once you have your Ears sorted
out, now what do you do with it?
The possibilities are numerous.

Sometimes while operating I might

want to check the WWV space
weather forecast(s) (at :18 & :45
minutes past the hour).

In the 1000mp, I have ALL of the WWV & CHU frequencies memo'd, in order,
so they are easy to bring up.


Because the sub-receiver is intended for in band reception, the WWV signal strength will be seriously attenuated; however from my usual operating location WWV is always S9+ on one or more of the memo'd frequencies.   Normally, WWV is presented to my right ear.
For SO2-V purposes, the AF-REV button allows flopping the two ears.


If I am on 20, 15 or 10 meters, I sometimes want to make a listen to
the NCDXF beacon for that band.

On 10 meters, the entire 28.200 - 28.300 frequency range is LOADED with numerous propagation beacons.

The SUB-Rx is a PERFECT candidate for listening to beacons while running

a frequency or S&P'ing under VFO-A.

Another use for Dual receive in a single-mode contest is that it allows me to S&P with the right ear, while running a frequency in the left ear.


In multi-mode contests (such as QSO Parties and Field Day) with two VFO's I can run a CW frequency on VFO-A while using VFO-B to search and pounce SSB contacts.

Now, all this takes practice, like learning to walk and chew bubble gum. Work your way up to full blown operation by spending hours practicing JUST RECEIVING with a VFO for each ear.


Testing the MFJ 752-C & JPS NIR-12 together

The N1MM+ logging software has done an incredible job of implementing Single-OP 2-VFO (SO2-V).

N1MM's design is such that EACH sub-window in the software can be moved anywhere you choose.

When I run SO2-V I tend to use an N1MM+ configuration something

akin to the picture below.



Notice that EACH VFO has a Data Entry Window and a Bandmap.  Many operators prefer to get rid
of the bandmap for Radio A as they are running a frequency there and not S&P'ing from that VFO.
I actually PREFER to keep Bandmap-A on the screen as it allows me to be on the constant lookout for 3rd-party stations moving in on what was previously a "Clear" RUN frequency.


Some people tell me they easily get too confused so dual-receive and SO2-V is just not for them.
That sometimes happens to me when running a frequency with a lineup of stations waiting to work me. Bottom line: if I get TOO confused, I switch out the sub receiver and regain my sanity by
focusing ONLY on running the frequency with VFO-A. Practice makes perfect.


In a mixed mode contest (such as a state QSO party, the 10-meter contest or Field Day) Receiver
A & B can be leveraged into working BOTH modes; the "primary" mode being in the left ear.

In the 2016 SA-10 10 meter contest, I was running a frequency on 14.045 using VFO-A, while tuning around for SSB contacts up frequency using VFO-B. The end result was a 1st place (world-wide) finish using MIXED mode.


There are more things to be said about Single-OP 2 VFO's in contesting.
When I was operating as WP2/WQ6X from Radio Reef on St. Croix, at one point I was

running a frequency on SSB with VFO-A, while S&P'ing random stations on CW using VFO-B. 
MFJ 752-C & JPS NIR-12 in Actual Operation

The possibilities are quite varied when using DUAL VFO's, however it takes PRACTICE to make
it all operate smoothly. Equipment glitches on top of that can make things completely chaotic.

If at ANY time you find yourself out of synch with the two receivers or feeling FRANTIC, turn off
the sub receiver, re-focus and re-connect with the original RUN Frequency under VFO-A.

Things can degenerate dramatically if you don't know what you're doing.

Dual Receive can be a WONDERFUL tool, if you use it properly.

Use it properly, don't let it use you to Lose.




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