Thursday, May 22, 2014

Crunch Time

So there is a lot of hand wringing about the fact this radio (6300) has no preselector so I decided to give a quick real world test given the equipment I have on hand.  I was hit by lightning a few years ago and it took out a fair amount of equipment so I thinned the stuff on the desk considerably.  One radio I do have immediately available is my Elecraft K-1.  Yes Virginia even I own an Elecraft.  I fired it up on 40 M on the back 1/2 wave 40 M vertical.  This antenna ain't no quick n easy 'tenna buddy cheapo.  It's 60 ft tall with a matching network coil made out of #6 wire.  It's over 3000 ft of wire the longest being my 160 radials which are about 150ft long.  The 40 M tuner is on the left.

In the front is a 43 ft wire vertical hanging in a pine tree 

and this is my remote tuner, a MFJ 929 auto tuner fed with T bias 12 V on the coax in a 50 cal ammo can.

I use this antenna primarily as a receive antenna on 160 80 40 and 30  since I can tune it from the shack.  I can also cut the 12 v to get a broadband response by bypassing the tuner.  

The 43 ft antenna was chosen for the Flex 6300 and the tuner was bypassed.

I ran the K-1 up to 0.2 watts and here is its spectra as seen on the 6300

Note the transmitted signal is about -40 dBm or about 33 over S9.  It is here I loose the spitting (spurs) from the K-1  and I could easily carry on a contact with a station at -120 dBm (s1)  The transmitted signal K-1 is 9 khz away.

I tuned up the band a bit further and at 20 khz up the band from the K-1 transmitter I can no longer hear the first hint there is a 33 over signal being transmitted 175 ft from my rx antenna.  

Here is a shot of me listening to a station who is -117 dBm only 6 khz up from my K-1.  He is 100% Q5 copy.

I had to go do a couple of operations to pay for my kids college so I didn't get to the second part of this rest till I got home.  I had been scheming ways to get a stronger signal into my 6300's un-preselected front end.   I cranked up the power to 7 W on the K-1.

As you can see the spectra is far dirtier.   Note the signal is about -20 dBm or about 53 over s9.  I put the K-1 through my alpha and got this 

Same spectra but the signal in the 6300 is now about -5 dBm  Now I'm up to 68 over S9 and this represents 40 W of transmitted power from the K-1  The band was dead so I looked for the first station that was tweaking my panadaptor 

It was a SSB station about 100 khz up the band  His strength was about -100 dbm or S4

I hit the key on the K-1 and was still able to copy him Q5,  His signal was totally unaffected.  I could not tell my K-1 was transmitting even though I was sending 50 w of CW on an antenna 175 ft from my rx antenna.

That's about as drastic of a test as I can muster right now.  It none the less is I think a pretty amazing test.  All of the RF from 30 khz to 54 mhz including a signal 68 over S9 only 100 khz up the band on SSB no less and the rx is bullet proof.  Eventually I will get another rig on the bench capable of driving the alpha to 1500w.  If I was at a 100 w class field day site: on 40 M I could easily work S1 stations on CW with a SSB station 150 khz up the band and as long as his TX was clean and I wasn't on a spur, no problemo.   Given enough power I'm sure I could crush the front end BUT the loudest station I ever hear is Radio Havana on 6 mhz and the loudest I've ever heard them is - 37 dBm or s9 plus 37.  This test gives a real world example of how the radio works

Not bad for a radio that ain't got no front end much less a friggin' roofin' filter!!

73  W9OY

Someone on eham didn't believe my band noise on 160 so I thought I would include a shot for the record.  Look at the dBm reading in the flag.  My antenna is a 66 ft resonant vertical.