DIY TV Antenna 2.0 - Page 6 - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th April 2011, 10:20 PM   #51
DF96 is online now DF96  England
diyAudio Member
 
Join Date: May 2007
Sounds good. Modern chips take some of the fun out of RF design, but sometimes we don't want fun but just a unit that works and does a job well.
  Reply With Quote
Old 21st April 2015, 09:39 PM   #52
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Blog Entries: 1
Quote:
Originally Posted by tubelab.com View Post
Fired up the breadboarded first stage of my amp today. Very simple circuit. RFMD SPF-5122Z chip, 4 caps and a coil. I think I can eliminate all but the chip and one cap once I switch to DC up the coax cable.

Performance is as good as the data sheet says. NF is .5 db at VHF rising to .6db all the way up to 1.3 GHz and hitting .9db in the 2 to 2.5 GHz region. Gain is a slope from 26 db at 100 MHz (too much, but probably OK with the low antenna gain at VHF) to 20 db at 1GHz and 11 db at 2.5 GHz. Measured with an Agilent N8975A noise figure analyzer.

IIP3 is +8dbm at 100 MHz, +15dbm at 400 MHz, and +19dbm at 1GHz. Measured with two Agilent E4438C ESG's and an Agilent E4440A PSA.

Input return loss is at least -10db across the TV band and drops to -8 at 100 MHz. Measured with an HP 8753 network analyzer.
I plan to test both amps cascaded with 40 feet of cable between them before deployment.

I will not have much more time to play with this until after I return from my road trip in late May. Will hit the Dayton hamfest on the way home to collect more tubes, and other toys.
How did your amp turn out in practice George?
I want one!
__________________
Pete Basel
http://www.linkedin.com/in/petebasel
  Reply With Quote
Old 22nd April 2015, 02:08 PM   #53
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
I made two prototype boards 4 years ago. One had a 4 to 1 balun transformer on the input, and the other didn't.

I stuck the transformer version on the coat hanger antenna 2.0 to see what it would do. It was mounted outside at the antenna so the feedline losses would not add to the system noise figure. It rammed so much signal into the Radio Shack distribution amp that it was overloaded with its gain turned all the way down. I removed the distribution amp and connected the output up to one TV. The low noise amp allowed excellent reception of the two TV stations in Port Saint Lucie that were previously seen on the spectrum analyzer, but too week to be decoded by the TV set. There were a few new weak TV signals visible on the spectrum analyzer that were not visible before. The Radio Shack amp with 50 feet of cable in front of it had virtually no gain above 700 MHz but cellular LTE was very strong at 720 Mhz and two way radio and cellular CDMA were strong at 850 MHz. The new amp displayed all sorts of signals with the twin coat hanger antenna up to 2.4 GHz. IMD products were still visible on the spectrum analyzer from the strong local two way radio and cellular signals, but they were weaker than those produced in the Radio Shack amp

I removed the outside amp and returned the system to its previous configuration because I had no suitable enclosure for the outside amp. Since then I have not used either of the prototype amps. I lost my 41 year job at Motorola last year, packed up and moved 1200 miles north.

We had a new house built in rural West Virginia, and finally moved in two weeks ago. It will take me a while to build a new basement lab, then I can get back to building stuff again. For now those little amps are stuffed in a box somewhere. The locals tell me that there is NO antenna TV reception here, no cell phone either, so for now we are paying Comcast far too much money......my spectrum analyzer says that there is some hope, but only time , and amp or two, and antenna 3.0 will tell. It will be several months before I have time to experiment.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 22nd April 2015, 06:59 PM   #54
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Blog Entries: 1
Thanks very much for the update, very sorry to hear about your job, it sounds like you were the best engineer there.
I'm in Connecticut about 65 miles from the NYC area towers, part of the path is over water, and I'm getting decent reception with a fairly small Clearstream 2 antenna:
Antennas Direct C2 ClearStream2 Outdoor Digital HD TV Antenna With Winegard DS-3000 39 J-Mount (C2) from Solid Signal

I need a better antenna, and I get a small number of channels without an amp but with a CM-7777 I get most of the NY channels and a few local just because they are so strong. I'm not using a rotator:
Antennas Direct C2 ClearStream2 Outdoor Digital HD TV Antenna With Winegard DS-3000 39 J-Mount (C2) from Solid Signal

The CM-7777 seems to get good user reviews but I have a feeling that your amp is much better.

I'm getting just enough signal that I can split it with a passive splitter to two sets, an active distribution amp just overloads and probably has so much IM that it is just not workable.

It is still on my list to get one of the better commercial bow ties and then I hope to be able to split 3 or 4 ways, or perhaps an even better antenna. I have it in the attic by the way.
__________________
Pete Basel
http://www.linkedin.com/in/petebasel
  Reply With Quote
Old 22nd April 2015, 09:33 PM   #55
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Blog Entries: 1
Forgot to mention that I studied analog, digital and RF design in college but never really had a chance to use the RF. Amazed by how you just threw this together!
__________________
Pete Basel
http://www.linkedin.com/in/petebasel
  Reply With Quote
Old 22nd April 2015, 11:05 PM   #56
PB2 is offline PB2  United States
diyAudio Member
 
PB2's Avatar
 
Join Date: Sep 2004
Location: North East
Blog Entries: 1
Are you familiar with the discontinued CM-4251: ?
Channel Master 4251 Tribute Page

I'd think that someone could figure out a way to DIY a CM-4251 using different construction methods.

They say that the Stacked Super-G-1483 UHF antenna is almost as good:
Stacked Super-G-1483 UHF antenna collinear package

This page covers how some of the better antennas have gotten worse in later production:
Temporary page

The Super-G-1483 is a Hoverman design, here is an improved DIY version, the Gray-Hoverman:
http://www.digitalhome.ca/ota/superantenna/index.htm
__________________
Pete Basel
http://www.linkedin.com/in/petebasel

Last edited by PB2; 22nd April 2015 at 11:24 PM.
  Reply With Quote
Old 23rd April 2015, 01:35 AM   #57
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
it sounds like you were the best engineer there.
I was far from the best, but I worked far below my abilities. I did this on purpose to prolong my career. I chose to do the work that nobody else wanted to do, designing and building prototype high tech devices! I was good at it and I enjoyed my job, but the environment was changing, and it became clear to me that corporate wanted the older higher paid people out, and I found out that the building had been sold, so when corporate offered me a buyout, I said goodbye! After 41 years in the same place, I was well past my corporate expiration date.

About 3 weeks after signing my exit papers, most of my friends, including those who refused to sign, were laid off.


Quote:
Are you familiar with the discontinued CM-4251: ?
Yes, they were all over Miami.....to receive the blacked out Dolphins games from WINK TV channel 20 across the everglades in Fort Myers. Those things were out of my budget, so I had a home made 4 antenna Yagi array made with broom sticks and welding rod. This was in the early 70's. That ended when Tampa got an NFL team in 1976. WINK chose to broadcast the Bucs instead of the Dolphins. I built a C band dish in 1981.

Quote:
Forgot to mention that I studied analog, digital and RF design in college
I did things a bit backwards. I walked into Motorola in 1972 at age 20 to answer a "technicians wanted" ad in the Miami newspaper with only a high school diploma. Out of about 500 applicants, 3 of us were hired. The HR guy said that odds were 2 of us would be gone in a month, the turnover rate was that high. He was right.

20 years later, they paid me to go to college and get a degree. When I joined the advanced development group, they sent me to school for a masters degree. Neither included any RF course work.

Quote:
Amazed by how you just threw this together!
The amazing work was done by whoever designed the IC chip. It is 50 ohms in and 50 ohms out. The "amp" is just the chip, two 50 ohm striplines, and a blocking cap. You add a choke and a bypass cap if you don't want power through the output coax. 50 ohms is close enough to 75 ohms, so that the mismatch losses are about 0.5 db. Most of the details are given in the device data sheet. No fancy RF techniques needed. There are more and more "RF building blocks" types of chips like these appearing on the market every day.

Here in the middle of nowhere there are two VHF stations that "cover" this area IF you are on high ground. We are down in a "holler" where there is little RF period. If I climb the 100 foot hill behind our house with a portable TV, I can receive both of them. Channel 7 Wheeling has CBS and ABC. Channel 9 Steubenville has FOX and NBC.

I see two possibilities. I will make a Yagi cut for channel 8 and see if there is any signal to be found on the property somewhere. If that doesn't work out I can always design a repeater with a battery and a solar panel to go up on the hill. It will only need to transmit a few hundred feet, a few milliwatts of power is all that is needed, but DTV signals require extreme linearity.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
DIY FM Antenna DreadPirate Everything Else 9 26th March 2011 03:06 AM
DIY antenna Fry-kun Analog Line Level 3 24th May 2007 08:52 PM
amplified tv antenna karma Everything Else 2 23rd July 2004 01:48 AM
DIY : 27Mhz yagi antenna . darkm4n Parts 6 22nd April 2004 11:22 AM


New To Site? Need Help?

All times are GMT. The time now is 08:23 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2