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Minimally modified QCX-17 has been heard on 80, 60, 40, 30, 20, 17, 15, 12, 10m this UTC day !

n4qa at_hotmail.com
 

Simply by adding a jumper which shunts the on-board xmtr pa lpf, and using appropriate external filtering has allowed my otherwise stock QCX-17 to be heard on all bands 80 through 10m, inclusive, this UTC day.
QCX rigs are very versatile, indeed ! Thanks, Hans !

See:
http://reversebeacon.net/dxsd1/dxsd1.php?f=0&c=n4qa&t=dx

72 / 73,
Bill, N4QA

John AE5X
 

Bill, will your QCX be making an appearance in CQ-WPX this weekend?
--
John AE5X
https://ae5x.blogspot.com

n4qa at_hotmail.com
 

John,
I'd be happy to try a sked with you or anyone...so long as it doesn't clash with our 23rd anniversary celebration on Saturday...Heh heh heh.
72 / 73,
Bill, N4QA

Michael Sharp
 

Interesting!

No complaints here, but so many times when I was on the SKCC Sked page, a few of the Ops there would ask me if I wanted to try 20m or 30m when 40m was dead. I would have to decline the offer, telling them I was on a monoband QCX, stuck at 40m.

That being said...

Would it be possible to modify one of the QRP-Labs kits, like the Ultimate Relay Switched LPF kit http://qrp-labs.com/ultimatelpf.html or similar and get it to work in conjunction with the QCX?

A tri-band QCX would be pretty awesome, if it was a thing. I’m curious to know about your setup with the external filtering. Do you have an pictures of your setup?

73,
Michael
KD9MED

geoff M0ORE
 

A simple jumper will bypass the series elements of the filter but the shunt elements will still be in circuit.

On 24/05/2019 23:32, n4qa at_hotmail.com wrote:
Simply by adding a jumper which shunts the on-board xmtr pa lpf, and using appropriate external filtering has allowed my otherwise stock QCX-17 to be heard on all bands 80 through 10m, inclusive, this UTC day.
QCX rigs are very versatile, indeed ! Thanks, Hans !

See:
http://reversebeacon.net/dxsd1/dxsd1.php?f=0&c=n4qa&t=dx

72 / 73,
Bill, N4QA

n4qa at_hotmail.com
 

Right, you are, geoff.
In another thread - a few weeks ago - I said this:
"Looking at the  QCX schematic, I am considering lifting one end each of C27 & C28, and jumpering the C29 end of L3 to the rf connector end of L1."
And, that would be only a bit more involved.
But, I decided to implement the quick-and-dirty solution first.
It's certainly not elegant...but it does work well enough for the QCX-17 to be heard on all bands.
And, using external filters - I've had a herd of them for years - the resultant is legal emissions.
And, though I haven't taken the time to measure sensitivity or selectivity, the QCX-17 has enabled me to hear workable signals on all bands 80 through 10 meters as well.
72 / 73,
Bill, N4QA

n4qa at_hotmail.com
 

Michael,
I have no pictures but, just imagine an otherwise insulated wire jumper - 1.5 inches long -  interconnecting the junction of C27, L3 with the junction of C28, L1.
And, while I've homebrewed many lpf and bpf, my favorites are actually manufactured units.
72 / 73,
Bill, N4QA

Steve Johnston
 

Michael -

I doubt it is practical to interface the Ultimate a Relay Switched LPF kit to automatically choose the correct filter for the band in use, but it would be easy to connect a five position rotary switch to manually select the correct filter on the relay board.  Simple, elegant and inexpensive...

Steve WD8DAS

geoff M0ORE
 

I use a very simple device called PIC-A Switch which was an article in RadCom in Sept 2001. It uses a PIC to measure the frequency and then switches the filter appropriate to that frequency. It can be used to switch anything you like and can be powered via the coax if you want to switch aerials.

I don't know if it is still available on the web though.

Geoff

On 25/05/2019 17:47, Steve Johnston via Groups.Io wrote:
Michael -

I doubt it is practical to interface the Ultimate a Relay Switched LPF kit to automatically choose the correct filter for the band in use, but it would be easy to connect a five position rotary switch to manually select the correct filter on the relay board.  Simple, elegant and inexpensive...

Steve WD8DAS

Michael Sharp
 

OK, but what about the notorious T1 toroid? If one is going to mod their QCX as a Multiband QCX, should you initially wind T1 for 80m? (I’m thinking harmonics, like 40, 20, 10, etc...)

-Michael / KD9MED

Guido PE1NNZ
 

Michael,
With C1, C5, C8 removed and with T1 configured for 40m RX is working well for all bands, but the lower bands (80m, 160m) are a bit deaf. So initially wind T1 for 80m would do probably better.
With a LPF installed, higher band harmonics on RX are not really an issue in practice in my experience; but a LPF is recommended to prevent FM broadcast mixing products.
For LPF switching, I like KD1JVs minimalistic approach by using a few series DPDT slider switches to select the appropriate LPF. Another interesting way to switch LPFs is to use 1N4007 for swiching [1], were you can use the rectified RF + 12V at C30 to bias the diodes either forward or in reverse.
Guido

[1] https://www.qsl.net/in3otd/electronics/PIN_diodes/1N4007.html