Which Tuner?

[caribsailor24]

I'm planning on installing my Yaesu FT-897 on my Pacific Seacraft Dana. I thinking of the SGC sg-237. Is anyone using this tuner, or does anyone have other recommendations. While I'm at it, it has been suggested that I don't need an insulator at the bottom end of the backstay. Any comments on that?

Gil Steinfort, KP2U
Green Flash, Dana 147
Satellite Beach, Florida

[svinshallah]

The 237 should work fine for voice, but is under-rated (40w continuous) if you plan on using email.

The bottom of the antenna normally has to be "insulated" from ground because the usual arrangement makes the bottom of the antenna a high-voltage point. If you touch the bottom of the antenna when you are transmitting, you may not get killed but you will get a nasty jolt. A fiberglass hull under good conditions is often enough of an insulator, but when it gets wet and salty then maybe not.

[caribsailor24]

Thanks. I see your point about the 40 watts continuous. Although I'm not planning on email right now, that could change. I've done it before on other boats. My concern is not cost, but space. You may be aware that the Dana is a VERY small boat. I would buy the SG-230 in a minute, I've had it on a previous boat, but it's HUGE. I would even consider the sg-239 which is rated at 200 watts (80 watts continuous), but is not water proof. It would be mounted in a lazarette (spell check can not deal with that word) that would never get wet, but who knows?

I also appreciate your comments about the question of not insulating the bottom end of the back stay. My three previous boats all had insulators top and bottom, but it has often been suggested that the bottom one is not really needed if the backstay is not included in a grounding network.

Thanks again for your comments.

[Goudurix]

Hi Caribsailor,
I have been struggling for years with a Yaesu FC-40 autotuner. It has 100W power rating, and is indeed quite a lot smaller than the SGC-230.
But it was really bad at tuning all-band, due to a too limited impedance matching range.
The RF ground/counterpoise should be OK doing it "by the book".
I've tried countless wire lengths, parallel wires etc. and always some HAM bands were not tuneable...

I finally threw it out last year and installed an SGC-230 and it is a WORLD of difference...this tunes everything HAM and marine.
And yes I have had some trouble to fit it in where the yaesu FC-40 was before.
But don't make the compromise...the SGC-230 is THE tuner.

AS for skipping the lower insulator: if indeed the backstay is not grounded at its chainplate you can connect the tuner from the inside to the chainplate. I would recommend to put the tuner even right at the chainplate if possible.
Put some HD insulation on the lower 2.0 metres of the backstay.

If you have a backstay tensioner then I'm afraid you will have to bypass that with a wire jumper unless it measures out as electrically conducting well.

Jan

[svinshallah]

The SGC-239 will work fine. You should be able to go to a good electrical supply house and buy a plastic NEMA (yes, spelled right) box that will fit the tuner and some "water-proof" wire pass-through glands that will make the unit mostly water-resistant. A little silicone when you put the top on the box will take care of most of the rest of the problems. The bottom insulator is mostly a safety issue although if the hull gets wet and salty the tuner may have trouble if you feed at the chain-plate. If you have a backstay tensioner, good practice is to feed the antenna above it. And don't let anybody adjust it if you're on the radio.

[Cheechako]

I used the SG230 for email alot with no issues. Cant remember it's rating though.

[svinshallah]

The smaller SGC tuners have a lower continuous-power rating than the 230. That's one of the reasons that the 230 is physically bigger.

[Goudurix]

The SGC website states the same continuous rating (80W) for both SGC-239 and SGC-230.
Strange.

What is also VERY important is its impedance matching range....

One thing I know for sure is that the SGC-230 has a far wider matching range than the Yaesu FC-40.

Anyone having the (official manufacturer's) impedance matching ranges for

SGC-239
SGC-230

?

Jan

[El Pinguino]

All you need to know can be found here SGC Smartuner Comparison

@#2 and #3 40 watts continuous rating should be fine. I always wind the power back to a max of 20 watts for digital modes including Pactor. Re the 239 I have had one at my home QTH for the last ten years, out of doors in the weather under a squidpole. I simply fitted into a plastic box to waterproof it.

[El Pinguino]

How I weatherproofed my 239....... I didn't use cable glands but if you did it would be pretty close to waterproof.....

[Goudurix]

OK!
If indeed the SGC-239 has the same power rating as the SGC-230 it should do.
If not, than it would be a pity not to foresee a higher power capability for voice SSB but of course 100W voice is not continuous.

I am still interested to find out about the SGC-239 impedance/reactance matching range.

Once you hace cut (isolated) your backstay to a certain length you are really stuck if your ATU fails to tune some wanted frequency ranges....this is the experinece I had with the Yaesu FC-40 ATU.
Of course you can still increase or shorten the length of the final lead from backstay base to ATU....

I am very satisfied with the SGC-230's performance.

Jan

[El Pinguino]

I notice that they recommend a minimum of 40 foot if you are using a simple longwire with the 239.... that may be a deal breaker for some.
Frank

[Goudurix]

And even then it doesn't mean you will be able to tune every frequency between 3.3 and 30 Mhz.....

However, if aiming for the HAM bands (7 Mhz, 14 Mhz, 18 Mhz, 21 Mhz, 24.9 Mhz, 28.5 Mhz) I found out that a 9.2 m wire (this is isolated backstay portion or sloping wire PLUS the lead from it to the ATU) is a good length:

close to 1/4 wave on 40m
enough under 20m 1/2 wavelength

and for 15m it is about 0.625 WL or the "hald enf-de Zepp" length with maximal gain lobe and still low-take-off angle for DX.

Above 15m it starts to be a cloud warmer.

If I had to cut and isolate my backstay and for a given antenna tuner, I would:

- loosen the backstay and run it close to the mast
- hang a sloping wire from a spare halyard in the same position as the backstay, to find a good compromise wire length to reproduce aftwerwards with the backstay
(even if the wire diameter, copper wire vs stainless, etc will give lsightly different results)

...or install the SGC-230 it tunes nearly everything....

Jan

[El Pinguino]

Agreed re the frequencies commonly used... my home QTH squidpole is 9 metres and it tunes OK with the 239 but afloat if using sailmail you may want to get down to 2 megs... even the local ( marine band) cruising net is on 4 meg.

I'm getting good results afloat with an Icom AT 140 into a whip about 3 or 4 metres long... but that is straying off topic....

edited to add... at home I don't work below 7 meg

[Goudurix]

Well not completely off_topic....

Since antenna wire length is important also with SGC-239....

I use a "alternative backstay wire antenna" (copyright Bill Trayford).

I have 1 central backstay. I run a wire from a halyard to the starboard top side of the pushpit and from there with isolated standoffs to a through-hull connector to the lazarette. The SGC230 is directly at the inside part of the through-hull conncector.

Total length 9.2 metres = good range for HAM 40m-15m.

To favor lower frequencies I would use a 40-45 ft wire length.

Jan