PDA

View Full Version : Tuner in line when not needed, no bypass



N1VAU
02-09-2013, 10:18 PM
I have a nice Dentron "Super Tuner" and currently a 40/20 meter fan antenna that I'm using.

This old tuner has no "bypass" so my choices are:
1. leave it inline even when it's not needed
2. take it out when not needed (PITA)
3. Get the drill and install a toggle switch bypass

I'm looking for opinions and reasons for them.
Thanks,
Clayton
~N1VAU

KH2G
02-09-2013, 10:30 PM
I like option 2 because it is one less item to give future problems. If your antenna starts acting up, without the tuner to correct the problem you'll get out there and fix it sooner.
73
Dick KH2G

N1VAU
02-09-2013, 10:41 PM
I should have mentioned I'm using it on other bands it doesn't otherwise tune up on. :o
~Clayton
N1VAU

KA5S
02-10-2013, 12:33 AM
I have a very nice Murch 2000A picked up recently, and if I can find where I put my (or can buy another) three circuit ceramic switch , a long shaft, with the switct on the back to select either tuned or straight through will allow a workable and professional looking solution.

Cortland
KA5S

AF6LJ
02-10-2013, 12:36 AM
If your antenna is not balanced MFJ makes a switch that can be used to bypass tuners etc...

WA7PRC
02-10-2013, 01:50 AM
If your antenna is not balanced MFJ makes a switch that can be used to bypass tuners etc...
That would be the MFJ-1703 (http://www.mfjenterprises.com/Product.php?productid=MFJ-1703), intended to interface 2 rigs to 2 antennas.
However, it appears it could be used to switch a tuner in/out:
http://www.mfjenterprises.com/pictures/MFJ-1703.jpg
Connect xcvr to Port A, antenna to Port 1, tuner input to Port 2, tuner output to Port B.
No holes needed to be drilled. It's rated 300W.

NA7U
02-10-2013, 01:29 PM
Or you can do the same thing by joining two 1x2 antenna switches together. Join the two single port sides with a 2x female coupler. Likely you can get more than 300W capacity that way.

W5DXP
02-10-2013, 02:54 PM
If your antenna is not balanced MFJ makes a switch that can be used to bypass tuners etc...

I have a series capacitor in an aluminum box that I switch in to allow 80m no-tuner operation on my ZS6BKW. I simply short the capacitor out for normal operation on other bands. What would happen if one installed a SPST switch that simply shorted the tuner's input to output?

AF6LJ
02-10-2013, 04:30 PM
I have a series capacitor in an aluminum box that I switch in to allow 80m no-tuner operation on my ZS6BKW. I simply short the capacitor out for normal operation on other bands. What would happen if one installed a SPST switch that simply shorted the tuner's input to output?

I would assume that if one shorted the tuner's output to it's input with a switch the tuner's L component would still be in the circuit. You would end up with a shunt inductance across the feedline. I was thinking of the MFJ product above when I made the post. I should have explained myself better :)

WB2WIK
02-10-2013, 06:16 PM
I'd install a bypass switch inside the tuner, there's room for it.

I've done this with every tuner I ever owned that didn't have a bypass provision. Usually I use a ceramic rotary switch mounted near the rear panel (inside) with a long enough shaft (or a shaft coupling and extension) and 1/4" panel bearing to bring the shaft through the front panel, and install a knob on that. A good quality switch will allow legal-limit power as long as it's not turned while transmitting (!).

Costs maybe $15 or so, takes an hour.

AF6LJ
02-11-2013, 04:11 AM
I'd install a bypass switch inside the tuner, there's room for it.

I've done this with every tuner I ever owned that didn't have a bypass provision. Usually I use a ceramic rotary switch mounted near the rear panel (inside) with a long enough shaft (or a shaft coupling and extension) and 1/4" panel bearing to bring the shaft through the front panel, and install a knob on that. A good quality switch will allow legal-limit power as long as it's not turned while transmitting (!).

Costs maybe $15 or so, takes an hour.

I am with you on this, my concern is not knowing the OP's technical savvy or access to the required tools I proposed a one size fits all solution anybody could make work.

It is easily enough done and makes a good "first project" installing a bypass switch into a tuner such as the one above.

N1VAU
02-11-2013, 01:32 PM
I'd install a bypass switch inside the tuner, there's room for it.

I've done this with every tuner I ever owned that didn't have a bypass provision. Usually I use a ceramic rotary switch mounted near the rear panel (inside) with a long enough shaft (or a shaft coupling and extension) and 1/4" panel bearing to bring the shaft through the front panel, and install a knob on that. A good quality switch will allow legal-limit power as long as it's not turned while transmitting (!).

Costs maybe $15 or so, takes an hour.

Where do I get one?
Thanks,
~Clayton
N1VAU

WB2WIK
02-11-2013, 05:46 PM
Where do I get one?
Thanks,
~Clayton
N1VAU

Here are some: http://www.surplussales.com/rf/rfcerrot_6.html

The "4-wafer" switch is cheap and you can remove two of the wafers to make it much "shorter." You'd need to make an L-bracket with a hole in it to support the switch way back behind the front panel, then use an ordinary 1/4" panel bearing to support the shaft where it comes through the panel.

That latter item can be found here: http://www.surplussales.com/ShaftHardware/ShaftH-9.html
Scroll down to P/N (SHW) SFTBUSH

This is an easy job.

KB1NXE
02-11-2013, 07:02 PM
If you don't want to mod the tuner, you can always make a bypass out of two - two position coax switches. Rig to the common of one of the switches, one output ot the tuner, the other to a piece of coax. The tuner output to ont of the switch positions of the second coax switch, and the bypass piece of coax to the other. Finally, the antenna to the common of the second switch. Both switches to the coax, and you're bypassed. Both to the tuner and the tuner is in line.

W5DXP
02-11-2013, 09:13 PM
I would assume that if one shorted the tuner's output to it's input with a switch the tuner's L component would still be in the circuit.

There should be a switch or roller setting for that inductance that will put a very high impedance across the line so that its effect would be negligible. Seems that inductive reactance could be adjusted for minimum SWR.

W9GB
02-11-2013, 09:36 PM
Here are some surplus rotary switches:
http://www.surplussales.com/rf/rfcerrot_6.html
Steve has referenced surplus CRL/CentraLab and Oak/Grigsby rotary switches.

IF you need any parts for modification or identify other available switches (used or new),
ElectroSwitch in Raleigh, NC acquired CRL/CentraLab in 1992 and Oak/Grigsby in 2003 switch products lines.
http://www.electro-nc.com/productpages/rotaryswitches.shtml

ElectroSwitch has a good distributor network (Mouser, Digi-Key, Allied, Newark, etc.)
The D4 series is a commonly stocked item.
http://www.electro-nc.com/dist.shtml

w9gb

AF6LJ
02-11-2013, 09:53 PM
There should be a switch or roller setting for that inductance that will put a very high impedance across the line so that its effect would be negligible. Seems that inductive reactance could be adjusted for minimum SWR.

That is true, one need remember to set the tap switch or roller inductor to maximum.

That works also.

ad: Sussex-1