HobbyPCB.com

Built by Hobbyist for Hobbyist!
It is currently Wed Aug 21, 2019 1:06 pm

All times are UTC - 5 hours




Post new topic Reply to topic  [ 2 posts ] 
Author Message
 Post subject: Demodulating AM
PostPosted: Thu Aug 09, 2018 6:19 am 
Offline

Joined: Thu Nov 17, 2016 6:58 pm
Posts: 32
A few times I've tried using my RS-HFIQ on 'nearby' shortwave broadcast bands (41m, 31m, 19m). What I've found, since there's 0 Hz LO offset in HDSDR, audio is distorted. I haven't played around with HDSDR enough to figure out how to set the offset properly, I thought I'd ask here. Would the same procedure apply if trying to transmit AM phone on the ham bands?

Thanks!

--Al

_________________
Al Holt
WD4AHB
EL89rt

Rigs/Radios: RS-HFIQ, Ultimate 3S, GenesisRadio G3020, SDRplay RSP1, Kenwood R-1000, Halli S-40B
Computer Hardware: Dell Inspiron 570 w/ Xonar DX
Software: HDSDR, OmniRig, com0com, VB-Audio, WSJT-X, FLDigi, SDRuno


Top
 Profile  
 
 Post subject: Re: Demodulating AM
PostPosted: Fri Aug 10, 2018 5:22 am 
Offline

Joined: Mon Jul 23, 2012 6:25 am
Posts: 1143
Hi Al,

Since both sound cards and the RS-HFIQ not no response at DC on TX or RX if the carrier of an AM signal is at the same frequency (+/- 20 Hz) it is eliminated.

So to run any mode that needs a response at the center (AM, FM) you'll need to offset the LO from the carrier by at least half the bandwidth of the signal. For AM, 4 kHz is probably a good value. In HDSDR go into Options > Misc Options > Set LO <-> Tuned Offset and enter 4000.

You can run SSB/CW etc with this offset as well but the soundcard/RS-HFIQ's performance is best at lower IQ frequencies.

73,
Jim WA2EUJ


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: Bing [Bot] and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group