Ham radio & single-sideband questiongreenspun.com : LUSENET : TimeBomb 2000 (Y2000) : One Thread
I have Realistic DX-380 AM/FM/MW/LW/SW portable receiver which I dearly love. The one drawback is it does not have single-sideband reception capability. Likewise with my Baygen Freeplay radio.
I somewhat understand that a signal contains an upper & lower sideband sandwiching the carrier wave. Is this correct? Anyway, can & would hams broadcast so that those of us with shortwave radios that do not have single-sideband reception are able to receive the signal ungarbled?
I assume this to be quite possible. What are the protocols of emergency broadcasting by hams regarding shortwave transmission. Please try to keep your responses worded for the electronically unsophisticated (read: dullard)!
-- Bingo1 (firstname.lastname@example.org), May 15, 1999
Bingo, During an emergency there will be two objectives.
B)use the mode that gives the best troughput ( greatest distance)
There are only a few transmission modes to to this.
SSB,CW,and some digital modes. None of them are receivable with your average AM radio.
For local use FM on the VHF UHF bands will be used and you will need to get a receiver for those frequencies. Older FM radios can be modified by removing the paralell capacitor in the input and at the oszillator. This will not be the most sensitive receiver but you will be able to listen to local repeaters ( those that are up and have power) Some of the wider band FM receiver that include the TV bands will be able to receive the 6m and 2m VHF bands.
-- Rickjohn (email@example.com), May 15, 1999.
Bingo, An few questions first. What kind of anrenna do you have? What kind of frequency protection do you have? Is you power line in protected against normal stray frequencies? Is this new to you and newly set up? If so would you be willing to go through the necessary, basic standaed steps necessary to know and use your aquipm3nt to the best of it's ability? Got code?
-- Cherri (firstname.lastname@example.org), May 15, 1999.
Thanks rickjohn. I was afraid of that. I can't afford to purchase another receiver. Dagnabit!
Notice I used the word receiver. This a key clue as to the answers I'm looking for.
Cherri: "What kind of anrenna do you have?"
I use the whip antenna mostly. I also have a long wire (60' +/-) which generally causes overmodulation.
Cherri: "What kind of frequency protection do you have?"
Neither receiver has synchronous detection, if that's what you mean.
Cherri: "Is you power line in protected against normal stray frequencies?"
No. Please elaborate.
Cherri: "Is this new to you and newly set up? If so would you be willing to go through the necessary, basic standaed steps necessary to know and use your aquipm3nt to the best of it's ability? Got code?" Got a spell checker?
-- Bingo1 (email@example.com), May 15, 1999.
Let's take these one at a time.
"I somewhat understand that a signal contains an upper & lower sideband sandwiching the carrier wave. Is this correct?"
More or less. A more detailed explanation would take more time and space than it is worth. If you really want to know the technical details, your public library probably has a section on basic radio, and if that doesn't work, try your local college library.
"Anyway, can & would hams broadcast so that those of us with shortwave radios that do not have single-sideband reception are able to receive the signal ungarbled?"
They could, but don't count on it. There are a few hams that like to play around with straight AM (which is what the SW stations use), but only for the novelty of it. You might find a ham somewhere that would be willing to transmit information from time to time in AM mode, but you would have a hard time finding one.
"I assume this to be quite possible."
Easily. It's hard to find a HF transceiver that doesn't have the capability to transmit in AM or SSB built into it, and selectable with a switch on the front panel.
"What are the protocols of emergency broadcasting by hams regarding shortwave transmission."
First, hams are not legally allowed to transmit outside the normal ham bands, except in the case of a FCC declared state of communications emergency. Many SW stations operate outside of those bands, so the hams have to stay out, or face possible legal action.
Hams are not allowed under most circumstances to broadcast in the same manner as a commercial broadcast station does. Ham transmissions are point-to-point type transmissions. The exceptions are few and far in between.
Protocols for ham radio operators are established by the FCC in 47CFR97, and by the ARRL. The ARRL protocols are not enforcable, and therefore non-binding. The FCC regs are partially rooted in ITU (International Telecommunications Union) rules and regs, and the FCC cooperates with the ITU.
If you want to know more about the ARRL protocols during emergencies, you can go to their web site at:
and use the search engine to get to the Public Service Communications Manual (PSCM). It's extensive, and written for hams, but it's free, and you can download it, if you wish.
-- LP (firstname.lastname@example.org), May 15, 1999.
If you have the time and patience, you can actually build low-cost receivers for the ham bands that will pick up SSB and CW transmissions for about $20 (or less). There are several kits available from different suppliers, the best, low cost (IMO) ones are made by Ten-Tec (they have a simple receiver kit that covers a good bit of the HF shortwave bands -- it's NOT very good for standard AM reception).
-- Dean -- from (almost) Duh Moines (email@example.com), May 15, 1999.
"There are several kits available from different suppliers, the best, low cost (IMO) ones are made by Ten-Tec "
Do you have a link (URL) for Ten-Tec? Sounds interesting!
-- Anonymous99 (Anonymous99@Anonymous99.xxx), May 15, 1999.
Thanks LP. I view the ability to receive ham transmissions as a must in case of potential emergencies such as Y2K may bring us. What to do, what to do! Guess I should've purchased the Sangean 803A instead of the Realistic DX-380!
Dean: Good suggestion. I've never undertaken any build-it-yourself electronics projects. Don't own a soldering tool. The price is right, though! I can follow directions, so what do you think? Are these kits for the novice? Do you have any URLs for me?
All advice is appreciated.
-- Bingo1 (firstname.lastname@example.org), May 15, 1999.
I recenctly purchase a Sangean ATS818 with SSB. I thought I'd turn radio on and voilia!....SW radio listening. I probably need an antenna 'cause nothing is too clear or I don't know where the SW English station are or when they are broadcasting. Guess I had high expectations.
-- Quietly (Quietly@lurking.com), May 15, 1999.
AM is too inefficient to use on shortwave, SSB is much much better and that's why hams switched to it years ago. FM is used on VHF and UHF since here, the distance traveled is usually much less. (sideband is available too for long distance work)
The easiest way to find good signals to listen to is to scan the two meter band (if you live in a large city) from 144MHz to 148MHz. Or if you like, you can buy the repeater directory which lists all the repeaters in the US by state and county. You can buy the directory at
or from Amazon books online.
If you do want to listen to sideband ham radio signals on shortwave, you'd best put up an outside antenna since most of the signals arent anywhere near as strong as the broadcast stuff.
-- spank (email@example.com), May 15, 1999.
This subject comes up from time to time, so I'll anticipate the next sub-topic before I forget about it with the following URL:
It's the website for the online version of the Shortwave Listening Guide. You can get a program listing for a wide variety of subjects and stations.
-- LP (firstname.lastname@example.org), May 16, 1999.
SSB is demodulated by mixing a second signal with the SSB signal to provide a carrier signal to give a complete signal for the demodulating circuits. I used to add my second signal as follows (this does work, try it before you scoff):
1 Put a cheap am transistor receiver as close to the shortwave as possible.
2 Turn on the cheapy (volume down as low as possible) whilst trying to receive a SSB signal.
3 Tune the cheapy around the dial until you hear a whistle/squeal from the shortwave. Then tune the cheapy VERY slowly until the SSB transmission comes clear.
Reason this works - cheap receivers are notorious for putting out a lot of interference. You just tuned the interference to the right frequency to add the correct signal to the SSB signal to demodulate the darn thing. Technique takes a little patience to master - and you want an AM cheapy that has a fairly decent tuning dial - not one that shifts a bit whenever you take your hand away from the tuning knob.
-- Paul Davis (email@example.com), May 16, 1999.