Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 05-11-2013, 18:15   #16
Registered User

Join Date: Jan 2013
Location: San Francisco Bay
Boat: Olson 34
Posts: 60
Quote:
Originally Posted by GWB View Post
Does anyone have any experience with this? I'm a ham and would like to purchase an Icom-718, but of course this is a 100 watt radio.
Does the Pactor modem require the full 150 watts....? I guess it would just make it a bit more reliable...? This is on a sailboat that will be sailing for Hawaii next year.
Thanks for any input
Suggest you make sure it is well ventalated as pactor has a very high duty cycle.
__________________

__________________
brianb00 is offline   Reply With Quote
Old 06-11-2013, 14:14   #17
GWB
Registered User

Join Date: Sep 2008
Location: Brookings, Oregon
Boat: Westsail 32
Posts: 296
Images: 1
Re: Pactor with 100 Watt radio?

Point taken, thanks Brian
__________________

__________________
GWB is offline   Reply With Quote
Old 06-11-2013, 19:59   #18
Sponsoring Vendor
 
Neptune's Gear's Avatar

Community Sponsor

Join Date: Oct 2012
Location: Gulf Harbour, New Zealand
Boat: Farr Phase 4, 12.8m
Posts: 992
Re: Pactor with 100 Watt radio?

Exactly the setup I have 718 with a Pactor 3. No issues at all over the last 20,000 miles...
Neptune's Gear is offline   Reply With Quote
Old 07-11-2013, 08:06   #19
Registered User
 
ka4wja's Avatar

Join Date: May 2007
Location: Florida
Boat: Catalina 470
Posts: 2,033
Re: Pactor with 100 Watt radio?

While I agree that keeping the rig away from bulkheads, etc. and allowing for adequate ventilation IS a good idea....
"PACTOR" is not really a "high-duty-cycle" mode...
Quote:
Originally Posted by brianb00 View Post
Suggest you make sure it is well ventalated as pactor has a very high duty cycle.
a) PACTOR-I (which is FSK) IS a 100% duty-cycle mode, but is used only to signal/connect with a station ( a few seconds), and then you're going to be using PACTOR-II or PACTOR-III...

b) PACTOR-II is actually approx. a 50% duty-cycle mode (about what an SSB transmission is with speech processing)...

c) PACTOR-III's duty-cycle varies, depending on connection quality (link s/n), with stronger signals being a very light duty-cycle of about 30%...and under very bad conditions, a duty-cycle of about 60%....



{Normal SSB transmissions without any speech processing, are typically 25% - 35% duty-cycle....and with speech processing, about 50% - 60%....}



Again, ensuring adequate ventilation for the radio IS important, but be aware that the "duty-cycle" of most sailors' PACTOR transmissions are not much different from an SSB transmission with speech processing....and sometimes even lower...


After typing this last night....I wanted to find some supporting material, so as not cause an argument....so, I waited 'til I found an obvious source: Sailmail...

Here is directly from the Sailmail website:
Quote:
FSK (frequency shift keying) is the transmission mode (used in Pactor-I) that the KAM+ uses all of the time, and that the SCS PTC-II uses briefly before it automatically switches to Pactor-II mode which uses PSK (phase shift keying). FSK mode has the potential to operate your radio continuously at maximum output. For engineers, its crest factor is 1.0 (i.e. the peak and average voltages of the modulating signal are the same).
PSK is the transmission mode used in Pactor-II and Pactor-III that is used by the SCS PTC-II after it connects with the SailMail station. When your radio is running at its peak output transmitting Pactor-II, its average power output will be half of its peak output. This is due to the properties of the PSK modulation, not due to any shortcoming of the radio. View this as an advantage of Pactor-II; it uses less power than does the FSK modulation used by Pactor-I (KAM+), and works over longer ranges at faster rates. For engineers, the voltage crest factor of the PSK used in Pactor-II is 1.45 (i.e. the peak to average voltage ratio is 1.45, which means that the peak to average power ratio is 1.45 squared, which is 2). A big advantage of Pactor-II, with its lower average power output, is that radios designed for voice duty can perform nearly as well as continuous-duty radios.
The crest factor of Pactor-III varies depending on how many tones the modem decides to use. Depending on the number of tones, the voltage crest factor for Pactor-III ranges from 1.24 to 1.93 (which corresponds to power crest factor of 1.9 dB to 3.7 dB). Remember by comparison that FSK has a voltage crest factor of 1.0 and Pactor-II had a voltage crest factor of 1.45. So in terrific conditions, Pactor-III, will use all 18 tones and will be very easy on your radio and only run your (150 watt peak power) radio at an average power of 40 watts. In lousy conditions Pactor-III will only use two tones, and with a 1.24 voltage crest factor will run your (150 watt peak power) radio at an average power of 97 watts.


I hope this helps...

John
s/v Annie Laurie
__________________
ka4wja is offline   Reply With Quote
Old 07-11-2013, 09:19   #20
Registered User
 
Cpt Pat's Avatar

Join Date: Feb 2012
Boat: Pearson Ariel, 26 feet
Posts: 158
Re: Pactor with 100 Watt radio?

In addition to the issues of heat dissipation at the high duty cycle demanded of the radio, you may also experience voltage sag from your battery bank. At 100 watts output, expect 20 to 25 amps current drain. If your battery bank voltage sags below about 11.9 volts under that load, you will see your transmitter output power begin to drop.

I use a "battery booster" (buck regulator) to keep the voltage above 12.0 volts into the radio. I don't have the luxury of running an engine to keep the battery bank at full voltage while transmitting.
__________________
Cpt Pat is offline   Reply With Quote
Old 07-11-2013, 09:46   #21
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,369
Re: Pactor with 100 Watt radio?

I used a Kenwood TS 450 in two boats. It is 100 watts. The pactor was great, better than many actually. But I was only in the Caribe. Who knows in timbuktu.....
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 07-11-2013, 09:54   #22
Registered User

Join Date: Sep 2008
Location: Camden, ME
Boat: A Thistle and a Hallberg-Rassy 36
Posts: 664
I use a boost regulator (a "buck regulator" steps voltage down) to feed my Icom IC-7000 ham radio on the boat, but the boat's M-802 is more tolerant of lower supply voltages.

Using a boost regulator is not a bad idea for any radio however. In an emergency, when battery voltage may be a lot lower than you normally let it fall to, a boost regulator may be able to keep your radio operational for longer.

I use one from TG Electronics. MFJ also makes them, and there are probably others.

Chip
__________________
SoonerSailor is offline   Reply With Quote
Old 07-11-2013, 10:51   #23
Registered User
 
Cpt Pat's Avatar

Join Date: Feb 2012
Boat: Pearson Ariel, 26 feet
Posts: 158
Re: Pactor with 100 Watt radio?

Quote:
Originally Posted by SoonerSailor View Post
I use a boost regulator (a "buck regulator" steps voltage down) to feed my Icom IC-7000 ham radio on the boat, but the boat's M-802 is more tolerant of lower supply voltages.

Using a boost regulator is not a bad idea for any radio however. In an emergency, when battery voltage may be a lot lower than you normally let it fall to, a boost regulator may be able to keep your radio operational for longer.

I use one from TG Electronics. MFJ also makes them, and there are probably others.

Chip
Yep. I'm also using the TG Electronics regulator. I'm also using another one for my Raymarine autopilot, and it no longer reboots when I transmit.

I agree it's a good thing to have in case of emergency. It's good to know that your radio will still work after your bilge pumps have nearly drained the battery.
__________________

__________________
Cpt Pat is offline   Reply With Quote
Reply

Tags
pactor, radio

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:23.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.