Discussion in 'Amplitude Modulation' started by N2DTS, Nov 21, 2019.
What modern radio isn't boring?
Well, I would say my Flex 5000 is fun to play with, there is a LOT you can do with it besides talk into it....
Apache Labs rigs can be an ongoing experiment. Open source with a variety of software and firmware. You can go as far down the rabbit hole as you want.
I have long thought that having a microprocessor pre-determine a range of functions is a lot less "fun" than leaving it up to the user to sort out how to get the best "radio" out of their equipment. Plate LOAD and TUNE controls are like the f-stop and shutter controls on a non-automatic camera.
I have noticed several complain about the SMD parts in modern radios. And statements that if it has SMD it can't be repaired.
While I agree that you can run into parts availability issues with some of the chips, the bulk of the parts are still standard stuff that can be purchased from a supply house.
As far as soldering them with your 60 year old 100 watt iron, with a 3/8 wide tip... no that ain't gonna work. But there is stuff available that will allow you to rework and repair the boards.
I am just guessing, but I would assume that these same complaints were launched when fiberglass circuit boards first made an appearance and began replacing the direct wire method of manufacture.
And the idea of these little transistors, as opposed to vacuum tubes HAD to have brought out the pitch folks and torches, that the manufactures were going to ruin the hobby by going to solid state parts and away from tubes.
Things change folks... And there is a long standing promise of change happening as sure as death and taxes.
And the truth is that I would rather try to track down some 100 plus pin surface mount IC than to attempt to locate and purchase an AM modulation transformer for some 60 year old Collins HF rig.
As I mentioned early on in the thread. SDR makes things easier, depending on access. With the old rigs, you got out the schematic and changed parts to increase the audio bandwidth.
With the SDR radio, you just go key in a number and load the configuration to the radio and your bandwidth is changed.
Now HOW it makes the AM is vastly different. But actually is in line with the current broadcast transmitter technology.
In the past the carrier was created at a fixed level and the plate voltage went though a transformer that was driven by an audio amplifier that was of the same output power as the RF.
With the SDR and solid state broadcast stuff the carrier is created with the AM in it, and the output stages only amplify it. THe carrier is created at different levels dependent on the AM modulation and that goes into the IF for the carrier and is mixed to the output frequency, already having both the carrier and the AM component modulation superimposed on the carrier.
Yes, it's different, but so was solid state technology in the 60's and 70's when we were building radios for discarded TV sets
No. Linear amplifiers are far too inefficient in Broadcast AM.
The only TX using that method that I ever saw was designed in the 1930's. Low level modulator with linear amps. Gave about 30kW but consumed about 250kW of power.
All now use switching techniques to achieve AM at high level. Modern AM TX's hardly need any cooling, they are so efficient.
The way you wrote this, you lead me to believe you've troubleshot down to surface mount components, found a source of supply for those components, and then removed/replaced surface mount components (100 plus pin chips) to bring the radio back up to "working like new" again. How many times have you done this, what radios, and what components?
Modern radios are now disposable since it's no longer economically feasible to repair them unless you have access to a cheap source of LRUs--Lowest Replaceable Units--that's what the manufacturers call them--the 3 or 4 major sub-assemblies that make up a modern radio today. The cost of running an LRU over a wave soldering machine has made repairing these LRU economically unfeasible to fix for at least 20 years now.
Heck, I don't even save my Icoms for parts any more. As soon as something starts go wonky on them, I scrap 'em.
Gates brought out a rig in the 1960s called the Vanguard that was a 1 KW AM rig that essentially consisted of a low power exciter driving a linear RF amp using a ceramic exposed anode tube with around 3000 watts plate dissipation. It was a dismal failure, hated by the techs who had to keep them on the air because it was a PITA to keep going within its design parameters. There were two versions, the Vang. 1 and Vang. 2. The 1 looked like a motel ice machine. The 2 looked more like a normal bc rig but the industry knew plate modulation was the way to go for that power level, rapidly followed by tube class D, then solid state.
Solid state makes sense for broadcasting on one frequency around the clock. It doesn't necessarily make sense for shortwave ham radio that is occasional and widely frequency varying.
What doesn't work here is condescending hyperbole.
That doesn't mean we have to go along.
I'd rather go for the mod. iron because I know where to look.
Why do you want hifi on transmit? That is just wasting bandwidth. Ham radio is for voice communications, not for high fidelity.
Bill - K5MIL
You are never going to change the thought process of those who are resistant to change.
They are going to keep on poo-pooing the solid state amps, the SDR radio's and everything else that doesn't include big iron and multiple tubes.
Especially the ones who have never owned or operated one.
I have nothing against big tubes and iron, I own a Gates BC-1G and enjoy using it.
It's like the battle between ford and Chevy owners.