UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Closed Thread
 
Thread Tools
Old 25th Feb 2020, 2:13 pm   #21
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
Default Re: Large Value Inductor Question

If it's amplifying an AM-modulated carrier, the amplifier needs to be operating linearly. Class-A or (at a pinch) class-B, but definitely not class-C!
G6Tanuki is offline  
Old 25th Feb 2020, 2:16 pm   #22
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
Default Re: Large Value Inductor Question

Quote:
Originally Posted by PsychMan View Post
With regards SRF, Kalee and others. My understanding of SRF is that you want the inductors maximum SRF to be considerably HIGHER than the frequencies it will see, is that correct to say? As above the max SRF it will not behave as an inductor?
Sometimes, but other times it simply does not matter.

Consider a simple mains transformer. SRF is likely to be around 5kHz. With typical primary inductance 10H (giving 80mA magnetising current), that implies a winding capacitance of 20nF.

Now suppose that the core manufacturer found some fantastic new alloy, same price, which upped the inductance to 1,000,000H of all transformers it was used in, with no other effects.

It's easy to see the world would be delighted, magnetising currents would disappear to practically zero. It's also easy to see that the new SRF would be 0.35Hz. We're running at 50Hz!! But does it matter? No.

In the current example, if the choke's SRF is a bit below the operating frequency, it just means a little readjustment of the ATU. And if the SRF is below operating frequency, not because of high stray capacitances, but because of a super-high permeability core, then that readjustment will be miniscule.

Where it might matter, is if there is feedback. Changing an inductive reactance to capacitive may make the difference between stability and instability. But in this circuit... Nope.
kalee20 is offline  
Old 25th Feb 2020, 5:20 pm   #23
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: Large Value Inductor Question

If you want a couple of proper RF transistors one rung up the power ladder, PM me an address and I'll stick a couple of 2N3866 in a jiffy bag for you.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 25th Feb 2020, 7:53 pm   #24
Skywave
Rest in Peace
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
Thumbs up Re: Large Value Inductor Question

Ah yes! The good ol' 2N3866. I first met these during a project in 1967 - and have been using them, albeit occasionally, ever since.

Al.
Skywave is offline  
Old 26th Feb 2020, 11:28 am   #25
PsychMan
Octode
 
PsychMan's Avatar
 
Join Date: Jun 2013
Location: Fleet, Hampshire, UK
Posts: 1,764
Default Re: Large Value Inductor Question

Thanks very much for that David, have sent you a PM. I’ll have a look online at some circuits using them
PsychMan is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:16 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.