Ham radio operators please read

[btrayfors]

There are some gems and some very misleading statements in several of the above posts. And, some red herrings.

1. As Rick said, there are good reasons for having BOTH a ham and a marine SSB aboard these days. I won't elaborate here, for sake of brevity; there are posts on the SSCA board which make the case.

2. Virtually ALL SSB radios aboard small vessels these days -- ham or marine -- are powered by 12 volts. The discussion about 115VAC power supplies and generators is a red herring. It's almost never involved.

3. Marine rigs, in general, are more tolerant of low input voltages than are, e.g., many ham rigs. Once input voltage drops -- for whatever reason -- below a threshold level for that particular radio it begins to behave erratically or to just quit. Typically, an HF set will begin "FM-ing", or distorting the voice signal. Most ham rigs are designed to operate at voltages normally found in cars, i.e., 13.6 or 13.8 volts (with the motor running); they're happy with voltages plus or minus 10%, but not much more. Marine rigs generally have 15% or more tolerance.

4. Some ham rigs are very good in this respect, and will operate down to voltages as low as will marine rigs. And, there are good solutions, like the W4RRY booster which delivers 13.6 volts to the radio with battery voltages as low as about 11 VDC. I've used this wonderful little device on my boat for a couple of years now. See, e.g., Gallery :: W4RRY Leo's Battery Booster

5. The discussion about voltage drop is interesting, but not complete. Yes, quality fuses have lower voltage drops than do bi-metal circuit breakers. And, fuses provide better protection for the radio than do circuit breakers. And, they are more reliable (less prone to failure). Still, circuit breakers may be OK in addition to fuses, since the amount of voltage drop at the typical loads presented by a SSB radio are very small. Usually, the prime culprits in voltage drop occurrences is inadequate size wiring and poor connections, not fuses and circuit breakers.

6. As Rick said, fuses or circuit breakers belong NEAR THE BATTERY. And, contrary to what Rick said, one isn't enough. You need to fuse BOTH the positive and the negative leads to a SSB radio.

7. The discussion re: fixed and variable PEP levels is ...well...misleading (I'm trying to be nice). Both marine and ham radios use similar PEP levels...generally between 100 and 150 watts...and in most cases the user can choose to reduce the output power (many commercial radios have a LOW-MED-HIGH power setting, while many ham rigs have a continuously variable RF power level adjustment). Mostly, users don't touch these....the radios operate at their rated output levels most of the time.

Bill

[Rick]

Many marine and HAM rigs are rated to operate (meet spec) with input voltages down to 11.6, 11.7 V. Many of these rigs that I have tested meet specs down to 11.0 V (but don't count on it).

Many installation problems have been traced to wiring the rigs via the customary installed dc distribution panel that has a breaker for the rig, and a main dc breaker for the panel and then another breaker or fuse from a house battery, also with a switch in-line with the battery and fuse.

HAM rigs operating at rated PEP may draw 20A. It does not matter that the current is a peak value or not because the IR drops in the typical dc panel installation mentioned DO cause a significant drop at these current peaks and, although one might complain that the ship's wiring is marginal or undersized for this, that does not ameloriate the problem of time degradation of all the intermediate connections in the current loop (don't forget ground) which ALSO includes power and ground drops due to things like bilge pumps cutting in. As a result it is recommended, IN GENERAL, to not use the ship's normal dc panel and distribution system (including the ground dc distribution system. Instead, wire the rig directly to a battery using approved wiring and fuses (yeah, one is supposed to put a fuse in the ground side of the rig not for personal safety but supposedly for the safety of the rig and coax).

Regardless, it is a rare installation that uses the ships dc panel that delivers a good terminal voltage to the rig at peak power. Keep in mind here that to meet spec for the rig with a somewhat depleted "house" battery driving it you essentially have NO voltage burden budget left over for the panel distribution wiring losses! This is my point. It doesn't matter that most of the time everything seems O.K. As an engineer I design to spec, not to what seems O.K., average, or most of the time.

As Bill suggests, it could be a good idea to use a buck/boost switcher supply to feed the rig. Make sure that the noise spec is good;not to degrade Rx S/N ratio across the band(s), and that it truly will deliver 20A peak outut current without sagging drive voltage.

[btrayfors]

Absolutely agree with Rick about wiring SSB sets -- ham and marine -- directly to the battery, using appropriate fusing devices on both positive and negative leads. I do this routinely, even with booster devices available. The distribution panels and breakers and wiring in typical installations aboard boats are insufficient for SSB needs AND....as important...introduce unwanted noise into the receiver and RF back into the panels.

Bill

[S/V Illusion]

Although an interesting read, none of the above few posts (discussing voltage) is relevant to the issue(s) brought up in terms of the ambient noise floor from radiated or conducted noise sources. I have no problem that we got off-topic but didn't want others to infer any of this will help their noise problems.