Hi MS100 amigo Marcelo (seguiré en inglés para los otros),
Don't worry there are solutions.....
Firstly you should decide which bands you need (HAM - which bands and/or marine SSB
- which bands?).
Secondly, the simplest solution is also the cheapest: do not cut your backstay but install an "alternate backstay antenna" (copyright Bill B. Trayfors
) => run a stainless steel or tinned insulated steel antenna wire from masttop (using a spare halyard) to the railing on the back of the boat (choose the side where you can install the antenna tuner just below the deck
as close as possible to where your antenna wire comes down e.g. the lazarette). I installed an insulated through-hull connector, and fixed the antenna tuner just below it, so I have no stretch of antenna wire running belowdecks (see pics on my page on QRZ.COM - just type in my callsign: ON3ZTT )
If you have this, and an RF counterpoise
connected also to the antenna tuner, you can easily play around with different antenna wire lengths (use cheap
copper wire for testing, replacing it with more robust wire later...yes of course for the purists....other wire insulated or not will change the velocity factor a bit but the effect won't be huge...).
Now determine the upper frequency limit you need for long distance SSB
- this will determine the max wire length: 0,63 X highest wavelength = maximum wire length. 0.63 times wavelength gives the highest gain lobes still with low take-off angle for long range communication. If you make it longer, you will mainly get RF radiation shooting up to the sky - useless for long range skip communication.
A practical example: say you want to use HAM 40m ,30m, 20m, 17m and even 15m as DX frequencies: a 8.9 meter wire will still give you low take-off angle for 21.25 Mhz (15m band). On 40m band it is slightly shorter than 1/4 wave so would still work well as a 1/4 wave groundplane antenna.
I found empirically that a 9.2m wire (sloping wire + the wire leading down from antenna wire until the tuner) gives me tunable allband use from 80m-15m HAM bands with the FC-40.
Say you want 4.4 Mhz till 12.5 Mhz marine bands: a 15.1 meter wire will still give you low-angle take-off and a 15m wire is also slightly shorter than 1/4 wave on 4.4 Mhz.
By the way at my home I have set up a 9.2 meter vertical whip antenna with elevated radials as RF counterpoise
, now using the CG-3000 antenna tuner and this also tunes well on the same HAM bands (80m - 15m).
This 9.2 metres is not a length specifically inked to the Yaesu FC-40 tuner but it must simply be a length where for which the resistance and reactances presented to the tuner are accceptable and within range, even for the FC-40.
Now if you would need both HAM bands and marine SSB bands, you could have 2 wires, interchangeable.
BTW these backstay wire solutions with an antenna tuner are always a compromise solution. You could have a far more efficient system without the need for a tuner using vertical wire dipoles also hoisted from the mast
but you would need one dipole per frequency.... I have 20m, 17m and 15m HAM-band homebuilt dipoles on board (sorry Bill: WITH 1:1 balun...) but I don't use them too often, the allband wire/tuner solution is more handy though less efficient.
Good luck, and do install the FT857 and FC40! Once you have the correct antenna length, the FC40 works superfast and reliable.