It is if it’s a receiving system 
Very good, Compton. I’m looking forward to the photographic proof section of this weekend. Archive mode, good one. 
We all need to remember that the PEP of a nominally 25w AM signal is actually 100w. (That is how the old 150w input power was translated to 600w PEP at the peak of the modulation envelope, and from there was translated into being equivalent to 400w PEP output for an SSB transmitter, assuming 66% efficiency for the final amplifier stage.)
The 20w PEP limit on an amplifier therefore means the carrier level of a 100% modulated AM signal should not be greater than 5W. Exceeding the rated carrier level will mean modulation will cause distortion of the RF signal and that means splatter! Lots of it! And possibly - destruction of the amplifier output devices due to exceeding their voltage ratings.
The 817 is rated at 2w output on AM - the PEP level is 8W at that setting. Be careful not to exceed the peak envelope limits of your radio or your amplifier.
The same kind of caution should be observed by 100w and 400 or 1000 watt home stations. 1000w PEP means a carrier of no more than 250w… Then you still need to consider whether a 1 minute transmission at that carrier level is viable for your final amplfier stage, from a power dissipation perspective. Many older tube radios would not be happy even at a carrier of 25% - insufficient disipation in the final tubes especially sweep tubes in the ft101 etc. The 6146s in ts520/820 and 101Z were better but still only had 25w each.
Home stations last year showed a range of modulation levels. Some had insufficient carrier and could only be copied on an ssb receiver. I used vfo A on AM and vfo B on LSB on the same carrier frequency for such signals. This is mainly due to people generally not using AM on those radios and not being aware of how to set them up optimally.
I found the AM reception and transmission of the 817 was surprisingly good especially on vhf bands without selective fading and adjacent channel qrm.
73
Andrew VK1DA/VK2UH
An aditional rule. Fibreglass squid poles are banned, must use bamboo.
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The FT101 is a strange transceiver on AM as the operator reinserts the carrier manually with a level control. Not always the easiest to set correctly.
FT102 used 6146’s - not as common as the 101.
Jonathan
Decent length bamboos can only be found in botanical gardens in this country, but I suppose we could go withying before an activation - anybody got a decent pollarded willow?
Brian
Around 1969 - 1970, carpets were always supplied by the wholesaler rolled up on a sturdy bamboo pole, approximately 15 ft in length. When I lived in London at that time, there happened to be a carpet retailer just across the road from my QTH, so I had an almost unlimited supply of bamboo poles for portable expeditions and even for use as masts for VHF/UHF yagis on the rooftop!
Happy days!
As for AM … whatever next? Spark CW?
73,
Walt (G3NYY)
Lots of radio hobbyists still use AM. Just listen to 6.2 to 6.4MHz at a weekend, or 1.610 to 1.670MHz in the evenings…
Or just listen between 108 -137 Mhz where it’s used professionally, for a very good reason, 24 hours a day!
Add 6070 KHz to Tom’s list - 10KW of AM, from a legal broadcast station owned and run by Rainer DB8QC - Channel292.
Now I wonder if I could borrow that amp one weekend - that’ll fix the 40m QRMers once and for all. Hmm might be a bit heavy to get up the hilltop (not to mention the power supply!).
Ed.
Would you care to share with us the “very good reason” that AM is used for Air Traffic Control at VHF?
73,
Walt (G3NYY)
That’s one of the strange things in the various models of FT101. Another is the clarifier (RIT) centre setting pot, which in some versions was mounted on the side of the final compartment, where it heats up and drifts. The 101 was renowned for not transceiving properly, ie. The frequency changed from rx to Tx by a small offset amount, which changed, sometimes a positive offset and sometimes negative, depending on how hot the final stage was. A “Wonderful radio”… Two operators with ft101Bs could wander all over the band as they tried to track each other. Many knew the rx RIT was not reliably zero but thought they knew which side of centre was correct, so they using the rig with the clarifier on all the time, usually set to the left or right of centre, by 1/10th of the width of the white line, mostly. So they could not be sure whether they were calling you on frequency or not. And usually were not.
Then there was changing side bands but merely switching the BFO from one side of the IF filter to the other, effectively changing the dial frequency. But we can’t blame them for not using PLL technology in those days. The Trio-Kenwood TS820 was the first design to solve that problem by including the BFO and the VFO in the PLL loop. Changing the BFO frequency automatically changed the VFO frequency by a compensating amount.
(It’s such a pity we hung onto LSB at all - the commercials standardised on USB and we should have too though inverting satellites would have been difficult to use)
Nostalgia is so passé.
There are lots of versions of the very good reasons. It is somewhere between “transition from AM would be complicated and dangerous” to “AM has better performance at low SNR than FM” or maybe “multiple callers mix linearly, unlike FM” as well as “powered aircraft don’t need a power-efficient mode like SSB”. In general, VHF AM is working just fine for civil aviation.
All of those are true.
They do use SSB on HF, but that might be due to spectrum space issues.
wunder
AM is legal, but spark is not.
And AM is easily copied by anyone using a simple receiver.
But if it doesn’t appeal, that’s fine. It’s intended only to have some fun doing something a little different. It won’t take over the entire band (for long).
73
Andrew VK1DA/VK2UH
I’m looking forward to WORLD SOTA straight key CW day or weekend.
Both, activators and chasers would have to be working on straight key.
Any votes for it?
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In my case that would be QLF day!
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What does QLF mean?
Is it for an English expression?
It matches perfectly an expression in Spanish I’m thinking on, but it’s too rude to be posted here.
QLF - I am sending with my left foot.
QLF? - Are you sending with your left foot?
Yes I’m up for that. Wonder how many would join in…
The primary reason is because the alternative, FM, suffers from capture effect.
This is a major problem with multiple stations sharing a single channel.
A strong FM signal would block all lower strength stations.
It’s basically a manual CSMA/CD system!
Doubling (CD) is instantly recognized by other listening stations because of the heterodyne.
Also, AM does not suffer from doppler distortion which modulation in the frequency domain does.
Pete
The version I read somewhere was somewhat less polite. it was a comment on the other station’s current code quality.
QLF: try sending with your left foot awhile.
