Bus Bar?

[muttskie]

Originally Posted by ka4wja

Bottom line here, for John (the original poster), and everyone else....
1) Wire the SSB radio directly to the main house battery bank, with LARGE wire / appropriate terminals, and adequate fuses/breakers....
---or---
[B]2) Use a buss bar, wired as described in #1....[/B

John,
Thank you for the many posts educating us about so many SSB issues. I have read most, if not all, of your postings over these last few years.
I have a question about wiring directly to the house bank as described. Is it detrimental to wire the large gauge wire from the radio to the load side of the primary battery bank fuse? I have a 420 AH house bank going into 2/0 cable (approximately 15 feet, one way to the positive buss) with a 250A class T fuse located about 10" from the battery post. I envision connecting AWG 4 cable to the load side of that Class T fuse holder through a 125A terminal fuse (at that location) with a one way run of about 18 feet to the radio. Of course the radio connection end will be fused appropriately for an ICOM M-802 installation. Comments?
Thanks,
Bill

[ka4wja]

Bill,
Sounds good!
John
s/v Annie Laurie

[muttskie]

Originally Posted by ka4wja

Bill,
Sounds good!
John
s/v Annie Laurie

Ok, Thanks.
Bill

[ka4wja]

An ironic situation has come up....with the John, the original poster just asking about 12vdc power wiring for his SSB radio, just a few days ago, and then yesterday I was asked about the M-802's current draw by an radio engineer....
Things are conspiring to make this info available to a lot of folks...

In a nutshell, the M-802 will draw approx. 30 amps peak, on transmit.... (slightly less with higher voltage and slightly more if your batteries are low)...
Yes, that's a lot...but thankfully we're not transmitting for long periods of time, so the actual "A/H's" used by the radio is small....
BUT...
But, in order to allow excellent performance, you must figure this "30 amp" draw into your calculations for sizing and length of the power wires, connection terminals, buss bars, etc....

Here is the detail info....enjoy...


Working with a ham radio manufacturer who is looking into improving their transceiver's transmit IMD, he mentioned that it seems the M-802 used a fair amount more power than typical "100-watt" ham rigs did, and asked me if I had the current draw figures (which I did for the most part, but I went ahead and did a new round of tests..)

Here are the Icom M-802 current draw figures (normal production run tolerances might be reflected in other M-802's having minor variations on different bands/freqs, but overall these should be very close for all M-802's...)

The stand-by and receive current draw...
Under stand-by, radio turned off, the TCXO draws about 100-110ma (~0.1amps), and on receive w/ audio, in all modes, it draws about 2.1 amps....all at 13.7vdc


My M-802 is run off a large (1125 A/H) battery bank, charged via a large solar array....and early this morning the battery voltage was 13.7vdc....a short run of 2ga wire powers the radio, with typ. max voltage drop of about 2%...giving me about 13.3-13.4vdc at the radio this morning, at the max current draw of 29.4 amps...


So, here are the overall current draws of the radio on the various bands (subtract 2.1 amps, the current draw in receive, for transmitter-only current draw), at approx. 140-150 watts output...

The zero-signal, mic-keyed but no modulation, current draw was 5.4 to 5.5 amps on all bands, 160m - 10m...


Band ```` SSB-whistle````` FSK Carrier (PACTOR-I)
160m````` 25.6amps`````` 25.6amps
80m ``````28.7 ````````` 28.7
40m ``````25.6`````````` 25.6
20m ``````28.7``````````28.8
17m```````24.7 `````````24.6
15m```````29.3 ``````````29.4
12m ``````24.4```````````24.3
10m ``````24.6``````````` 24.5

PACTOR-II is an approx. 50% duty-cycle mode, so "average" current draw in PACTOR-II would be about half of the FSK PACTOR-I figures....and PACTOR-III's duty-cycle varies from ~ 30% to ~65% (depending on speed), so your "average" current draw in P3, will be 30% - 65% of the FSK PACTOR-I figures...

(FYI, the M-802 is spec'd at 30 amps, max current draw @ 13.6vdc....and all of these figures are about typical for a 150-watt marine HF transceiver....and yes, that is more than your typical "100-watt" HF ham rig...)


All measurements were done near the radio, with a fairly new Klein clamp-on meter (which has proven to be within 0.1 amps of other meters I have tested it against), at ambient temp of about 70*F....with battery voltage of 13.7vdc, and voltage at radio of approx. 13.3-13.4vdc under full current draw of ~ 29amps...

So, when people tell 'ya that you need to figure on 30 amps of current draw from a Marine SSB radio, they are correct....judge and size your wiring run accordingly...



I hope this helps...



Fair winds to all....


John, KA4WJA
s/v Annie Laurie, WDB6927
MMSI# 366933110

[ka4wja]

Bill,
An 18' run of 4ga, should be "okay"....(although I usually recommend on size larger)
(I use 2 ga for a 4' run to a fuse/switch and then 2' - 3' of 00ga to the batteries...)

Originally Posted by muttskie

Ok, Thanks.
Bill

Just saying, I use larger....

But, using the 3% voltage drop chart, assuming a 30 amp draw...and a "round-trip" of 36', 4 ga should work....


Fair winds...

John
s/v Annie Laurie

[manitu]

Originally Posted by dohenyboy

2. As far as an SSB is concerned, I believe the manufacturer's instructions might be illuminating. The manual for the ICOM M802, which is a very good product, shows that the unit is internally fused with a 30 amp and a 5 amp fuse. Installers are advised to connect the head unit directly to a ship's battery ONLY utilizing the power cable supplied:
CATION:[sic] The supplied DC power cable MUST be
used to provide power to the transceiver. AVOID
exceeding the 3 m (10 ft.) length of the DC power
cable. When it is necessary to make a run of over
3 m, use #6 or similar weight cable instead of the
supplied DC power cable for a maximum of 6 m
(20 ft.).


Reference: page 55 of the manual, 2002 edition

The fuse/circuit breaker at the battery isnt for the radio but for the cable.
To prevent fire if the cable is compromised, you need a fuse at the source. Max 15cm/6" from the battery.

.manitu

[muttskie]

Originally Posted by ka4wja

Bill,
An 18' run of 4ga, should be "okay"....(although I usually recommend on size larger)
(I use 2 ga for a 4' run to a fuse/switch and then 2' - 3' of 00ga to the batteries...)

Just saying, I use larger....

But, using the 3% voltage drop chart, assuming a 30 amp draw...and a "round-trip" of 36', 4 ga should work....


Fair winds...

John
s/v Annie Laurie

Thank you for the update, John.
I haven't installed the cabling yet, so upsizing to AWG 2 would be easy.
Regards,
Bill