JNC cs-818 tuner

[MarkF]

I have a cs 818 tuner that will not tune a 10 meter random antenna with a 17 ft counterpoise. I can tune the wire antenna with an MFJ-945E manual tuner to an SWR of 1 to 1. Is there anything I can do to the antenna so that it will be able to be tuned by the cs-818?
Thanks/Mark

[N8TGQ]

Hi Mark-
A lot of auto tuners, and internal tuners in modern radios are not able to tune much more than a 3:1 SWR.
Maybe try a 9:1 transformer between the antenna and tuner:

http://www.earchi.org/proj_homebrew.html

This is not the same as a 49:1 transformer for end fed half wave antennas. Dont get them mixed up!

Another thing to try is change antenna length. Basic rule of thumb is "at least a quarter-wave long on the lowest band you want to work, and not a half-wave or muliple half-wave on any band you want to work". Your 10 meter antenna would be 1 halfwave on 20m and 2 halfwaves on 10 meters. Here's a page that gives good lengths. Use the longest you can fit in your space.

https://www.hamuniverse.com/randomwirea ... ngths.html

To me, playing with wire antennas is one of the best parts of ham radio!

Have fun!
Rick N8TGQ

[MarkF]

Thank you so much! I think the 9-1 transformer is the answer and will make one! Thank you and 73’s!

[Andrew (grayhat)]

Thank you so much! I think the 9-1 transformer is the answer and will make one! Thank you and 73’s!

follow this

http://vk6ysf.com/unun_9-1_v3.htm

for the 9:1, the toroid may be smaller for QRP as long as it can host the windings and is a #43 material, then also add a choke after the transformer, something like this

http://vk6ysf.com/balun_choke_balun_hf_reisert.htm

will suffice, as for antenna, see here

https://udel.edu/~mm/ham/randomWire/

HTH

[edit]

for portable use 35, 40, 60 and 70 ft may be fine, for permanent use pick some longer size fitting your available space

further infos

https://la9xga.com/?cat=63

viewtopic.php?t=19

[MarkF]

Great! I’ll add a choke to the line! I ordered the 9-1 Balun and it will be here Friday. Thank you for your help!
73’s,
Mark

[MarkF]

Just connected an LDG 9:1 unun to my random wire and it tuned up magically on all bands! 1.3 to 1 on 40 meters putting out 7 watts and 1.2 to 1 on 20 meters and 7 watts. Just made an easy QSO as well!

Next is to put in a common mode choke.

Thank you all so much for your help!
73’s,
Mark

[Andrew (grayhat)]

Just connected an LDG 9:1 unun to my random wire and it tuned up magically on all bands! 1.3 to 1 on 40 meters putting out 7 watts and 1.2 to 1 on 20 meters and 7 watts. Just made an easy QSO as well!

Good news, now consider making your radiator wire a bit longer, not too much by the way but if you can, with a 71ft (21.64m) wire you'll be able to cover all bands from 80 meters up and that will still be a pretty manageable size, for example such an antenna could be laid out as an inverted L using a telescopic rod and with the wire sloping away from the rod, see the attached image (no artwork) to have an idea

Next is to put in a common mode choke.

If you want, all you'll need is a #43 toroid (an FT140-43 will do), some thin coax, two connectors and a box to enclose the thing (and place the connectors), winding it is quite easy, just look here

https://www.dj0ip.de/rf-cmc-chokes/diff ... lla-choke/

the above will serve you well on all bands from 160 to 10 meters

Thank you all so much for your help!

Y/W and please keep this thread updated with your tests results after setting up the choke !

[Andrew (grayhat)]

regarding chokes, as I wrote, my reference design is the one from Rick (DJ0IP)

https://www.dj0ip.de/rf-cmc-chokes/diff ... lla-choke/

but that's for QRO and uses a quite heavy toroid (FT240...) which adds some weight to a portable kit, for QRP a 140 should suffice, going for a smaller one may probably be possible, but then there won't be room for the windings and due to the small size the windings will probably present inter-capacitance <sigh> anyhow, if someone is interested a good reference for CM chokes is this one

http://www.karinya.net/g3txq/chokes/

[Andrew (grayhat)]

Hi Mark-
A lot of auto tuners, and internal tuners in modern radios are not able to tune much more than a 3:1 SWR.
Maybe try a 9:1 transformer between the antenna and tuner:

http://www.earchi.org/proj_homebrew.html

This is not the same as a 49:1 transformer for end fed half wave antennas. Dont get them mixed up!

Your note about transformers ratio made me think... maybe it's a crazy idea, but imagine building a tapped transformer offering two transformation ratios, that is 9:1 and 49:1, now imagine having a 65ft (ok more or less) EFHW (on 40m), we connect the antenna to the 49:1 post, connect a counterpoise to the ground post and we're on air, but... we find that neither 40 nor 20 are in good shape, so... we connect to the end of our antenna a 6ft piece of wire, so reaching a total radiator length of 71ft which is one of the "good" lengths for random wire antenna, change the transformer post from the 49:1 to the 9:1 and jump on the air on whatever other band (from 80 to 10 meters), I think that such a transformer, with the addition of a piece of wire may be very useful during POTA activations and sometimes may even "save the day"

What do you think ?

[Brian - K3ES]

Andrew - It should be possible to wind 9:1 & 49:1 transformance ratios on the same toroid, using different tap points. A few thoughts:

First, if your ~66 ft radiator for 49:1 is tuned low in the CW range for 40m, it should be resonant on 20m, 15m, and 10m for CW. It would also likely be workable for SSB on those bands with a modest tuner.

Second, if you are resonant with 49:1 EFHW on 40, 20, 15 &10m, there might be no need to include them in the 9:1 EFRW repertoire.

Third, excluding 40, 20, 15 & 10 makes ~66 ft a good non-resonant "random" length for 80, 60, 30, 17, & 12m without need for adding length to the radiator.

Fourth, for use with higher bands (15 & 10m) an EFHW usually includes a capacitor (approximately 100 pf) across the input feedline. This would not be needed for the 9:1 EFRW function, so it could be desirable to switch it out of the circuit.

Finally, with a wide-range tuner, I have had success tuning a 40m EFHW on all bands from 80 to 10m (including 60m & WARC bands), so maybe the 9:1 is not needed after all...

With all that, it would be interesting to do the build and the test. Anybody willing to do the build?

Best 73 de Brian - K3ES