Relaying antenna reception - AVS Forum
Forum Jump: 
 
Thread Tools
Old 07-03-2013, 05:03 PM - Thread Starter
Member
 
reddog007's Avatar
 
Join Date: Apr 2013
Posts: 75
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 14
So my brother lives in nowhereville, KY. He lives in a deep valley. Only two stations we know will come in, and the other three potentially may need some fancy antenna if that were to even work.


Though there is a hill on his property that is over 1400ft, and you can see for miles up there. He could easily get 20 stations from all over up there with two or three good antennas. The only problem is the distance from the top of the hill to his house in the valley. Standard coax would be unrealistic.

If he were to stick antenna's up there, how would we be able to get what those antennas capture down to the house?

Can the antenna's feed into a dish that points LOS at another dish that is on the house? Would the isolated unit on the hill need to be powered?
Is there stuff that is already made to do this where we just have to piece together what we need?

Is seems like this should be possible, but is it too possible, especially on a reasonable budget?
reddog007 is offline  
Sponsored Links
Advertisement
 
Old 07-03-2013, 07:55 PM
AVS Special Member
 
holl_ands's Avatar
 
Join Date: Jun 2004
Location: San Diego, CA
Posts: 3,756
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 63 Post(s)
Liked: 69
This question was answered here:
http://www.digitalhome.ca/forum/showthread.php?p=1060579
and in this thread:
http://www.digitalhome.ca/forum/showthread.php?t=113236

In the first link, I cited Radio Mobile for calculating signal levels....that was before TVFool was available. To determine actual signal levels at the Repeater be sure to add the Receive Antenna Gain (in dBd = dBi - 2.15) to TVFool's calculated "RX(dBm)" level. To determine actual receive level at your house, take that number, increase it by the Preamp Gain (if used), decrease by Filter Losses, add Antenna Gain of both antennas and subtract the Line-Of-Sight Loss from the Repeater to your house.....simple Gain & Loss additions. Result should be 10+ dB BETTER than -85 dBm nominal ATSC Sensitivity.

Since the short path from the top of the hill to your house is line-of-sight, you probably don't need BIG TV Dishes, but fairly high Gain Antennas on that leg will help to suppress multipath and other possible interference to your neighbors. As you read through the Repeater Thread, you will also learn that Single Channel Filters (plural, plus RF Splitters & RF Combiners) should be used at the Repeater....which will force the use of an active Preamp (plus Solar Panel & Battery)....and these filters will also contribute a bit more to the overall degradaton of the digital waveform....which is why commercial implementations of On-Channel DTV Repeaters (e.g. Distributed DTV Transmission Networks are used as part of the new Mobile DTV systems) must be carefully engineered....and for rural users, a frequency shifting DTV Repeater technique is also available. And since they are professional products, they cost thousands of dollars plus engineering services costs.

Suggest you call around to various TV Installation Services companies and see if they can refer you to someone who provides these systems.
holl_ands is offline  
Old 07-03-2013, 11:13 PM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
holls_ands, you really need to read up on the history of CATV, and how it was originally done. No high power amps, no solar powered circuits, no high end antennas. You have a lot to learn in how it was done, and how it can work for the OP.

They never stated the distance from the peak of the mountain to the location of where the home is, so you are basically shooting off from the hip, assuming way too much, that they cannot make it work.
gregzoll is offline  
Old 07-04-2013, 08:07 AM
AVS Special Member
 
Wendell R. Breland's Avatar
 
Join Date: Sep 1999
Location: North Carolina
Posts: 4,419
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 63 Post(s)
Liked: 61
Quote:
Originally Posted by reddog007 View Post

He could easily get 20 stations from all over up there with two or three good antennas. The only problem is the distance from the top of the hill to his house in the valley. Standard coax would be unrealistic

Is seems like this should be possible, but is it too possible, especially on a reasonable budget?

You can use 300Ω Open Wire Feeder (a.k.a. Ladder Line) to go several hundred feet because it has much lower loss than coax. Don’t know if this type wire is still available.
Wendell R. Breland is online now  
Old 07-04-2013, 08:57 AM - Thread Starter
Member
 
reddog007's Avatar
 
Join Date: Apr 2013
Posts: 75
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Liked: 14
It is ~600meters LOS and ~1000meters from the house to the top of the hill taking the road that goes up there.
reddog007 is offline  
Old 07-04-2013, 10:12 AM
AVS Special Member
 
Wendell R. Breland's Avatar
 
Join Date: Sep 1999
Location: North Carolina
Posts: 4,419
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 63 Post(s)
Liked: 61
Quote:
Originally Posted by reddog007 View Post

It is ~600meters LOS and ~1000meters from the house to the top of the hill taking the road that goes up there.

For that distance the solution would be quite expensive because it would require repeaters or RF to fiber, or microwave. All of these are out of my area of expertise.

At one time we had our 10 meter dish connected to the IRD’s (C-Band) via 500 feet 1-1/4" heliax. It was a pain because the line had to be pressurized with nitrogen. In later years the heliax was replaced with RF to fiber.
Wendell R. Breland is online now  
Old 07-04-2013, 10:24 AM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
gregzoll is offline  
Old 07-04-2013, 01:24 PM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29
Quote:
Originally Posted by gregzoll View Post

holls_ands, you really need to read up on the history of CATV, and how it was originally done. No high power amps, no solar powered circuits, no high end antennas. You have a lot to learn in how it was done, and how it can work for the OP..

As I recall (or recall having once read) it was originally done on channels 2-6.

"Me, I live on toppa da hill, half way down"

- Common description of residence location of about three-fourths (pronounced: tree-forts) of the (da) population of Somersworth (summerswert), New Hampshire, AKA, The Hilltop City.
AntAltMike is offline  
Old 07-04-2013, 01:41 PM
AVS Special Member
 
Wendell R. Breland's Avatar
 
Join Date: Sep 1999
Location: North Carolina
Posts: 4,419
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 63 Post(s)
Liked: 61
Quote:
Originally Posted by gregzoll View Post

Now this may work http://www.vfmstore.com/trc12g.htm

No, that is a RF link that has just one composite video and mono audio capability.
Wendell R. Breland is online now  
Old 07-04-2013, 03:04 PM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
Quote:
Originally Posted by Wendell R. Breland View Post

Quote:
Originally Posted by gregzoll View Post

Now this may work http://www.vfmstore.com/trc12g.htm

No, that is a RF link that has just one composite video and mono audio capability.
Wendell, that is at least a start that we can come up with, for the OP situation. I think as a group we can all do this and help the OP out on a solution. I am wondering if they could place a shack up there for the equipment to convert the incoming signal through a RF Modulator and use the relay to send it down the mountain. Solar panel on the roof, and a battery bank for overnight power, with maybe a timer on it to shut down the system at night, when no one will be using it.

Have to think out of the box on this one.

I found another one, but the max range is 250M LOS. http://www.eyespyli.com/pv22lcdtvmonitor.htm Another that is rated at 1000m LOS http://www.amazon.com/HOSSEN%C2%AE-2-4GHz-Wireless-Transmitter-Receiver/dp/B0094NNBPA/ref=pd_sxp_grid_pt_0_2
gregzoll is offline  
Old 07-04-2013, 03:31 PM
AVS Special Member
 
ctdish's Avatar
 
Join Date: Dec 2000
Location: Mystic,CT,USA
Posts: 1,374
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Liked: 23
The vfmstore website has a disclaimer saying that some countries would not allow the use of a product like this. I am sure the US is one of these.
John
ctdish is offline  
Old 07-04-2013, 03:37 PM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
The OP will have to contact them, since all we can do is give them ideas of what is out there.
gregzoll is offline  
Old 07-04-2013, 03:52 PM
Member
 
mjd420nova's Avatar
 
Join Date: Aug 2012
Posts: 162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 20
This would be a challenging installation. I would go with a high grade coax, with a broadband (30 to 1500 MHZ) amplifier. RFI filters on both ends to eliminate any interference and a final amplifier before any splitter to feed the sets. Individual antennas for each major direction of origination points would be ideal but with that elevation, a smaller antenna might suffice. Proper grounding is essential, with lighning arrestors at both ends of the coax and a ground stake at each end, one at the antenna and the other where the coax enters the home. Geting the coax in place is a snap. I use 30 LB fishing line tied to an arrow. Insure there are no power lines between you and the installation location. Using a bow, shoot the line in the right direction and then pull the coax after tying a nylon leader on. This might be easier in smaller shots but getting the line back up in the trees at an intermediate point could be difficult but would insure an easy pull with less likelyhood the fish line will break as you get more coax suspended. Inexpensive solar panel powered units will handle the amplifier at the antenna and if an intermediate point is needed to add an amplifier. Using as long a run of coax as you can get as any splices, splitter, connector or barrell will reduce the signal strength, the less connectors the better.
mjd420nova is offline  
Old 07-04-2013, 03:57 PM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
I found this thread from 2009 on dtvusaforum.com http://www.dtvusaforum.com/dtv-hdtv-reception-antenna-discussion/3246-maximum-length-coax.html I am getting to the point, that the OP family member may be better off just going with Satellite TV, whether it is Dish, Direct, or C/KU-Band, than go through all of the costs associated with designing and maintaining something like this. They would at least need one maybe two amps along the run, and how much are they going to lose in the process, just so that they can get the antenna in a ideal location for better reception.
gregzoll is offline  
Old 07-04-2013, 05:24 PM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29
Does he have control of or use rights to the straight line path? These distances are nothing. .625 hardline loses 6.27 MHz per hundred meters at 600 MHz, and 7.09 dB at 750 MHz, Unless there is a great signal level differential between your strongest and weakest essential channels, all you would need with .625 hardline is the antenna preamp and one or two line powered line extenders. If you give us an optimal antenna location tvfool analysis, we can see how much of a challenge the differential in signal levels might present.

You can buy used, pull-out 750 MHz line extenders dirt cheap, because the cable industry quickly bypassed the 750 MHz system architecture.
AntAltMike is offline  
Old 07-04-2013, 05:42 PM
AVS Special Member
 
Wendell R. Breland's Avatar
 
Join Date: Sep 1999
Location: North Carolina
Posts: 4,419
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 63 Post(s)
Liked: 61
Quote:
Originally Posted by gregzoll View Post

Wendell, that is at least a start that we can come up with, for the OP situation.

The OP does not state it but it is assumed that his kin desires multiple stations and probably desires they remain in HD if they were originally so. If true, there is no inexpensive way to do this. There may be some units that are available that could heterodyne the TV channels to a lower frequency so the loss would not be as high over a long cable run and then be heterodyned back to their original frequency.

The first thing I would have to know is what the signal levels would be for the desired channels. Once that was known one could proceed to engineer a cable system if there was adequate signal levels available and willing to spend the money on cable, line amps, tilt compensators, etc. Of course it still may not be piratical to do using the best RG-11 cable and using hardline would be very expensive.
Wendell R. Breland is online now  
Old 07-04-2013, 08:16 PM
AVS Special Member
 
olyteddy's Avatar
 
Join Date: Oct 2005
Posts: 3,496
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 178 Post(s)
Liked: 259
How about a passive repeater using Yagis or other high gain directional antennas? 2 antennas on top of the hill connected together, one pointed toward transmitter to receive signal, second one pointed down the hill toward the house to send the received signal. Third antenna at the house pointed up the hill to the sending antenna.
olyteddy is offline  
Old 07-04-2013, 08:35 PM
 
gregzoll's Avatar
 
Join Date: Jun 2009
Posts: 2,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 32
Quote:
Originally Posted by olyteddy View Post

How about a passive repeater using Yagis or other high gain directional antennas? 2 antennas on top of the hill connected together, one pointed toward transmitter to receive signal, second one pointed down the hill toward the house to send the received signal. Third antenna at the house pointed up the hill to the sending antenna.
I forgot all about that. Did a quick search and found this http://www.matthewsworkbench.com/passive-tv-repeater/

http://www.cableserv.com/index.cfm?PID=85&PIDList=85&DSP=SubCategories&CategoryID=2&SubCatID=19
Article from 1994 on building one https://www.box.com/shared/ckfbf117io

This has been an interesting thread today. Got me to do some homework, even though it was for the OP, reminded me why I got into electronics as a kid, due to my father being a retired U.S. Air Force Radioman, and what I did in the Navy dealing with communication equipment and other equipment that we dealt with on a daily basis.
gregzoll is offline  
Old 07-05-2013, 04:38 AM
AVS Special Member
 
mikepier's Avatar
 
Join Date: Sep 2006
Location: Long Island and Upstate NY
Posts: 2,467
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked: 21
Reddog, just for curiousity can you post your tvfool results?
mikepier is offline  
Old 07-05-2013, 05:07 AM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29
I used to work on an MATV system that serviced a sprawling garden style apartment complex and broke its RG-11 trunkline into two distribution branches: one was well over 1000 feet long,maybe even closer to 1,500 feet, and it used Blonder Tongue extenders that were powered by 30 volts AC. Biggest PITA system I have ever had to service, though not for reasons that would afflict this poster. At each of seventy tap points, there was a Jerrold, outdoor two port tap, and the RG-11 was connected to each using feedthrough connectors, and the center conductors were secured by being wrapped around screw terminals so I had no convenient disconnect points for testing, but anyway...

One snag in designing such a long amplified antenna downlead is that over that length, you'd have to use AC, but all modern pre-amps use DC. I think Winegard was using AC for its cartridge mounted preamps in the 1970s, but even if there is an AC line powered preamp available, it wouldn't be operable on a 60 volt line, and might not even be safe to use on a 30 volt line even if one could drudge up enough 30 volt AC amplifiers for this trunkline, and I don't think I have ever seen a 30 volt amplifier rated above 450 MHz. Unless the OP is committed to receiving and sustaining a really weak signal, the difference in the noise factors between a low noise preamp and a clunky, AC powered line extender amp will be of no concern to him.

I don't know what the lower voltage threshold is for a typical 60 volt line extender. Does anyone here know that?
AntAltMike is offline  
Old 07-05-2013, 08:30 AM
AVS Special Member
 
olyteddy's Avatar
 
Join Date: Oct 2005
Posts: 3,496
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 178 Post(s)
Liked: 259
Quote:
Originally Posted by AntAltMike View Post

...

One snag in designing such a long amplified antenna downlead is that over that length, you'd have to use AC, but all modern pre-amps use DC. I think Winegard was using AC for its cartridge mounted preamps in the 1970s, but even if there is an AC line powered preamp available, it wouldn't be operable on a 60 volt line, and might not even be safe to use on a 30 volt line even if one could drudge up enough 30 volt AC amplifiers for this trunkline, and I don't think I have ever seen a 30 volt amplifier rated above 450 MHz. Unless the OP is committed to receiving and sustaining a really weak signal, the difference in the noise factors between a low noise preamp and a clunky, AC powered line extender amp will be of no concern to him.

I don't know what the lower voltage threshold is for a typical 60 volt line extender. Does anyone here know that?
AC is used to power CATV electronics mostly for convenience. The modules and other parts of a CATV amp run on DC, typically 24 volts. AC is used for power distribution because designing a regulated power supply with a wide range of input voltages is easier with an AC input, especially in the early days when they still used transformer based supplies. Modern amplifier supplies are switching supplies and could probably run just as well on DC. Another reason for AC is that by modifying the power company's Sine wave to a (nearly) square wave you can send power that is (nearly) as effective as DC. A 90 volt square wave is about the biggest you can push through class 2 wiring, I believe. The final reason for AC is electrolysis. The cable plant is an eclectic mix of metals (largely aluminum but also copper, zinc, steel, stainless steel and others) so by using AC damage from electrolysis is minimized. Most modern cable is powered by 90 Volts, but usually the input voltage range of equipment I've worked with (30, 60 and 90 Volt gear) has allowed as little as 50 to 60% nominal Voltage before there was a problem.
olyteddy is offline  
Old 07-05-2013, 03:27 PM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29
Quote:
Originally Posted by olyteddy View Post


AC is used for power distribution because designing a regulated power supply with a wide range of input voltages is easier with an AC input, especially in the early days when they still used transformer based supplies,
...by which I think you are referring to linear supplies.

I'm under the impression that modern switching power supplies are ordinarily engineered to deal with a wider range of inputs than are any common transformer-based supplies. Stand-alone switching regulators often have published input specs of about 80 to 250 VAC..
Quote:
Modern amplifier supplies are switching supplies and could probably run just as well on DC.

Maybe the switching regulator circuits I have analyzed are not modern, but I'm pretty sure that the first component in the input circuit is a transformer. I have seen some wound to step up and others wound to step down, but in neither case would DC pass through it. On the other hand, linear supplies designed for low voltage AC input ordinarily begin with a bridge rectifier, which could work with DC input if it was in the right voltage range.

About five years ago, I had to develop a bid for UHF signal distribution to 1,200 residential units in a five building condo complex, and at the time, I could get relatively old, used 60 VAC C-Cor 750 MHz line extender amps for thirty something dollars each, which is about one tenth what an individual would pay for new, modern units, so if those old units came with linear supplies instead of switching supplies, they would still be what we likely would be working with here.
Quote:
Another reason for AC is that by modifying the power company's Sine wave to a (nearly) square wave you can send power that is (nearly) as effective as DC. A 90 volt square wave is about the biggest you can push through class 2 wiring, I believe. The final reason for AC is electrolysis. The cable plant is an eclectic mix of metals (largely aluminum but also copper, zinc, steel, stainless steel and others) so by using AC damage from electrolysis is minimized. Most modern cable is powered by 90 Volts, but usually the input voltage range of equipment I've worked with (30, 60 and 90 Volt gear) has allowed as little as 50 to 60% nominal Voltage before there was a problem.

That emboldened type is what I was looking for, because if we eventually get enough info to try to kludge together a bargain-basement priced amplified downlead, there is going to be a hell of a lot of voltage drop over 600 meters of RG-11.

600 meters of RG-11 will lose close to 70dB at the top of the UHF broadcast band, so if there is no severe input signal strength or differential problem, he'd need no more than 3 inline amps, but the one nearest to the antenna would see a substantially lower voltage than would the one nearest to the residence. Estimating the voltage drop would be a crap shoot, because we likely will not be able to reliably estimate the current draw of the two intermediate or downstream amplifiers with the kind of precision that a cable system engineer is held to. Over 600 meters, I'd just drop in two or three 30 dB amps in an RG-11 line, with the proximity of the first one to the antenna to be determined by the range of signal levels coming off the antenna, and then play it by ear/eye from there.

The OP can buy a nice cheap Sencore 1453i meter on eBay for $75 (I bought two from them) and replace the battery pack for $30 to $40 and leave out a lot of guesswork.
AntAltMike is offline  
Old 07-05-2013, 04:02 PM
Advanced Member
 
retiredengineer's Avatar
 
Join Date: Aug 2007
Location: Anaheim, CA
Posts: 557
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 20
Quote:
Originally Posted by olyteddy View Post

How about a passive repeater using Yagis or other high gain directional antennas? 2 antennas on top of the hill connected together, one pointed toward transmitter to receive signal, second one pointed down the hill toward the house to send the received signal. Third antenna at the house pointed up the hill to the sending antenna.

If the OP decides to go with a passive repeater, there will be mutual pattern interference between the two antennas. That can be avoided by rotating the second antenna to vertical polarization and also rotating the third antenna to vertical polarization. This also reduces any possible multipath interference to his neighbors.
retiredengineer is offline  
Old 07-05-2013, 07:43 PM
AVS Special Member
 
olyteddy's Avatar
 
Join Date: Oct 2005
Posts: 3,496
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 178 Post(s)
Liked: 259
Quote:
Maybe the switching regulator circuits I have analyzed are not modern, but I'm pretty sure that the first component in the input circuit is a transformer.
I've seen plenty with DC input. Many have a series inductor on the input to keep the switching noise out of the power source, but start with a bridge rectifier. I suppose some may have an input transformer but that would be more for isolation from the mains. Typical Block Diagram:
olyteddy is offline  
Old 07-05-2013, 09:23 PM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29


But this is all academic. As far as I know, all cable TV line extender amps are designed to run on AC and I would expect are optiomized to run on AC, so there would be no reason to not run them on AC unless you absolutely had to have DC at a mast-mounted preamp, and even if he had to have DC for a preamp at the end, I'd rather kludge a rectifier circuit for the end of the line.
AntAltMike is offline  
Old 07-05-2013, 10:16 PM
AVS Special Member
 
olyteddy's Avatar
 
Join Date: Oct 2005
Posts: 3,496
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 178 Post(s)
Liked: 259
An excellent example of an isolated power supply. Are you sure it's a switching? It appears to me as linear circuitry and not PWM or any other switching circuit. I agree that AC is more convenient (especially if you can get 90 Volt equipment) but DC is very feasible too.

EDIT: If you used DC you could very well solar power it. Personally I'd try the passive repeater first.
olyteddy is offline  
Old 07-05-2013, 10:34 PM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29
Quote:
Originally Posted by olyteddy View Post

An excellent example of an isolated power supply. Are you sure it's a switching? It appears to me as linear circuitry and not PWM or any other switching circuit. I agree that AC is more convenient (especially if you can get 90 Volt equipment) but DC is very feasible too.
.
I just googled: switching + power + supply + images and took the first image of a schematic with a transformer on the input line that was convenient in size for posting frown.gif Tomorrow (today, actually), I'll try to make time to look at a few on my bench.

Upon further investigation, it may be some earlier hybrid switching design. Here is the text that accompanied that diagram:





The switching power supply, shown in the schematic, provides 12 volts, at 10 amps, maximum, using a discrete transistor regulator with an op-amp functioning as a comparator in the feedback circuit. The supply was constructed in 1984 and is variable frequency, as opposed to the pulse width modulator (PWM) controllers used today.

With reference to the schematic, the front panel power-on light is not shown. There is no adjustable current limiter in this unit, although R1, R2, R3, Q2, R8, R9, C5 and Q4 set the current limit to approximately 10 amps. As you can see, the design is very similar to that of a linear power supply, except that L1, and D1 have been added, and U1 operates in a switching mode as a comparator with a small amount of hystersis. The switching frequency of this unit varies with the output current drawn by the load. This is an undesireable feature, which is why PWM regulators are used today. With a PWM regulator, the switching frequency is constant and will produce spurs only at known discrete frequencies rather than spurs at all frequencies. The Darlington-connected pass transistor block in the schematic is there twice (in parallel) for robustness. R4 in an internal trim-pot that can set the output voltage anywhere between 5 to 15 volts.
AntAltMike is offline  
Old 07-06-2013, 06:28 AM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29
Quote:
Originally Posted by AntAltMike View Post

I used to work on an MATV system that serviced a sprawling garden style apartment complex and broke its RG-11 trunkline into two distribution into two branches: one was well over 1000 feet long,maybe even closer to 1,500 feet, and it used Blonder Tongue extenders that were powered by 30 volts AC. ...

Here's the baby we used in that system:


(Image link blocked: The link to the eBay listing, with illustration is here: http://www.ebay.com/itm/Blonder-Tongue-LP-30-CATV-Line-Extender-Amplifier-/360689517516?pt=LH_DefaultDomain_0&hash=item53fac543cc )

I may seek out an image elsewhere, but my prospects aren't good because all the images of it I found so far were in PDF format.

They were Blonder Tongue LP-30, had an external jumper for user selection of 30 volt line powering or external transformer powering, and someone is presently offering a "new" one on eBay for $49.99

Quote:
...I don't think I have ever seen a 30 volt amplifier rated above 450 MHz
.
Unfortunately, as the marking on the cover says, it only goes to 300 MHz.

If the OP is serious about developing a 60 volt trunkline cheap, I can contact a surplus broker who does not sell to the general public and see how cheap I can get some used 750 MHz, 60 VAC extenders. I think the ones I had priced out previously had 30dB of gain.
AntAltMike is offline  
Old 07-06-2013, 07:05 AM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,598
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 32 Post(s)
Liked: 29
Reddog007's profile page shows that he has not been online since he authored his post #5 here.
AntAltMike is offline  
Old 07-06-2013, 08:45 AM
AVS Special Member
 
Wendell R. Breland's Avatar
 
Join Date: Sep 1999
Location: North Carolina
Posts: 4,419
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 63 Post(s)
Liked: 61
Quote:
Originally Posted by olyteddy View Post

It appears to me as linear circuitry and not PWM or any other switching circuit.

The schematic depicts a straight ahead linear power supply that has a regulated output that is adjustable with R4.
Wendell R. Breland is online now  
 
Thread Tools


Forum Jump: 

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