Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: DVB-T as cheap and easy panadaptor and 2nd receiver for radios with VHF IF  (Read 7609 times)
K3CBC
Member

Posts: 2




Ignore
« on: April 08, 2013, 05:58:31 PM »

My FT-450D has a first IF of 67.899 MHz which is within the tuning range of the DVB-T dongle. I tapped off the output of the first mixer with a small capacitor and snuck a coax through the rear grille. I spliced the coax into the cable going to the DBV-T, plugged the DVB-T into the computer and the hardware part is done.

Using HDSDR, I now have a 2.4-MHz-wide panoramic display. HDSDR has a setting where you can enter the IF and any additional offset; in my case I use 67923000 Hz with a 24000 Hz offset, and I swap I & Q to reverse the frequency display. After trimming the frequency correction the display tracks the VFO perfectly. (Note that the display has zero at the center; not the actual receive frequency).

I can play any signal that is within the 2.4 MHz bandwidth through the computer by simply clicking on the display. By tuning the DVB-T separately, I can go a few MHz above and below the IF and still receive reasonably well.

This should work with any radio that has a high first IF. The trick is to avoid bandpass circuits. In the FT-450D, there is a low-Q tank circuit directly in parallel with the mixer output so there is some attenuation 20kHz either side of the center, but this seems to have little impact. The roofing filter immediately follows and any point after that would have a severely restricted bandwidth.

There was another similar posting earlier, but that was about using the DVB-T and an upconverter as a parallel receiver.
« Last Edit: April 08, 2013, 06:02:22 PM by K3CBC » Logged
WE1X
Member

Posts: 320




Ignore
« Reply #1 on: April 13, 2013, 05:08:21 AM »

Did something very similar with an Icom IC-7600 using a Terratec T Stick Plus dongle and HDSDR per Stefan's (VE4NSW) mod. This mod is non-invasive (no soldering, no drilling and completely reversible).  Details can be found on the 7600 Yahoo! Group. Works just great.
Logged
K4AX
Member

Posts: 33




Ignore
« Reply #2 on: April 13, 2013, 08:15:15 PM »

I played around with this yesterday with my Yeasu ft-857d.  I tapped the first I.F. at 68mhz, but of course it knocks down the receive on the rig big time when I split it with the RTL dongle  Receive on the dongle side isn't that hot either. I'd like to get it working on the Yeasu and be able to use the receiver on it and see the waterfall on the computer and use the computer as a second receiver when needed.  However, at this time I can't figure out exactly what I need to do to split the signal but keep it strong on both sides.
Logged
WE1X
Member

Posts: 320




Ignore
« Reply #3 on: April 14, 2013, 05:43:51 AM »

Clearly different radios. It's fortunate the 7600 mod is far simpler with no side effects. In the 7600 there is a cable that connects two jacks: (a) scope display and (b) the RF unit. This cable is removed and replaced by two cables that connect to a low loss splitter (Mini-Circuits 1552 ZFSC-2-1-S).  The dongle is connected to the splitter as well. This approach avoids any attenuation of the receive signal.  The dongle is used only to receive the 7600's 64.455 IF and drive the HDSDR software.

I was able to get this to work with SDR# and SDR-Radio Console v2 (technical preview...not quite a beta) as well.



Logged
WS4E
Member

Posts: 220




Ignore
« Reply #4 on: April 16, 2013, 07:49:45 PM »

If you have an FT-450 I would check out the MOD that I did to mine to add a softrock ensemble to work along with it.

http://ws4e.blogspot.com/2011/07/ft-450-sdr-interface-to-softrock.html
Logged
9A4QV
Member

Posts: 7




Ignore
« Reply #5 on: April 17, 2013, 01:17:22 PM »

I played around with this yesterday with my Yeasu ft-857d.  I tapped the first I.F. at 68mhz, but of course it knocks down the receive on the rig big time when I split it with the RTL dongle  Receive on the dongle side isn't that hot either.

Hello,
you probably overloaded the point where you tap the signal out. It is the question of high or low impedance tap point.

What I read on the experiments from the Italian guys, the FT-817 is working without any issue and problems, without degradation of the signal but I am not sure that they manage to do the same with the FT-857 or 897.

Check the site, the photos are quite self explanatory, I have no problems with Italian language but they write  (and talk) too much :-) so use the google translator for more info.

http://hamradio.selfip.com/i6ibe/panadapter/panadapter.htm
I have two of FT-817d but still did not make the mod. I have to do it before the microwave RS season..
Have fun..

Adam, 9A4QV
Logged
VE3TMT
Member

Posts: 387




Ignore
« Reply #6 on: June 14, 2013, 10:22:57 AM »

It works on the older rigs too. I tapped the 47 MHz IF in my Yaesu FT990 and like to the other poster I see well over 2 MHz on each band. Point and click and I'm there. You can see a screenshot on QRZ.com

VE3TMT
Logged
AE4RV
Member

Posts: 940


WWW

Ignore
« Reply #7 on: July 13, 2013, 03:21:13 PM »

Interesting about the Icom 7600 non-destructive mod. Is there a similar mod for the 7410? That would be great.
Logged
K1ZJH
Member

Posts: 949




Ignore
« Reply #8 on: July 22, 2013, 07:41:34 AM »

Thanks for the great suggestion. That might be a good way to get a panadaptor display for my Ten Tec Omni and Paragon rigs.

Pete Smiley
Logged
K1ZJH
Member

Posts: 949




Ignore
« Reply #9 on: August 01, 2013, 07:27:27 AM »

Out of curiosity, is this dongle a good candidate for a 70 MHz IF?   

http://www.amazon.com/NooElec-RTL-SDR-RTL2832U-Software-Packages/dp/B008S7AVTC/ref=sr_1_2?ie=UTF8&qid=1375366791&sr=8-2&keywords=sdr+radio

Also, is PowerSDR-IF a good program to use with the device?

Pete
Logged
VE3TMT
Member

Posts: 387




Ignore
« Reply #10 on: August 01, 2013, 11:51:01 AM »

Hi Pete,

Yes it will work. That is the one I use on my Yaesu FT990 on the 47.2 MHz IF. You just have to enter the proper IF frequency in the software. There are a couple of fine tuning settings but you set them once and forget about them. I use HDSDR and get about 2 MHz of bandwidth. Check out a screenshot on QRZ under my call.

Max
VE3TMT
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!