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post #1 of 10 Old 02-22-2019, 07:21 PM - Thread Starter
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Pre Amp for HD Radio Antenna?

Has anyone here ever experimented with using a pre-amp with an FM radio antenna? Where I live we are situated between two markets and pick up some of the stations in HD fine but some of the others are right on the fringes and sometimes come in and sometimes don't. I'm planning to try an outdoor FM antenna to see if that will improve reception. I've been toying with the idea of experimenting with a pre-amp if the antenna alone doesn't do the trick. I'm thinking the Kitz Technologies 501. It has a really low noise factor at .85 and it is adjustable so I don't overload the tuners. Anyone tried this before?
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post #2 of 10 Old 02-23-2019, 12:11 PM
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Are you sure the stations you're interested in hearing don't stream?

HD Radio is nice to have but broadcasters invest very little into the the programming. If you can pick up some HD stations with your tuner and stock antenna, great. But I personally wouldn't go to the kind of effort you're considering to pull in distant signals given today's streaming alternatives. And I say that as someone who once had a huge, directional rooftop FM antenna on a rotor with a Magnum preamp to pull in stations 100 miles away when radio was the primary way to discover new music. Those were the days.
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post #3 of 10 Old 02-23-2019, 06:36 PM - Thread Starter
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Pre Amp for HD Radio Antenna?

Quote:
Originally Posted by Carnivore View Post
Are you sure the stations you're interested in hearing don't stream?



HD Radio is nice to have but broadcasters invest very little into the the programming. If you can pick up some HD stations with your tuner and stock antenna, great. But I personally wouldn't go to the kind of effort you're considering to pull in distant signals given today's streaming alternatives. And I say that as someone who once had a huge, directional rooftop FM antenna on a rotor with a Magnum preamp to pull in stations 100 miles away when radio was the primary way to discover new music. Those were the days.


The problem with streaming is rights issues.. most sports leagues don’t allow streaming now unless you subscribe to their out of market packages. Station streams are required to air alternative programming during games. Most stations in my area don’t have good quality streams either.. 64kbps is a rare thing around here. Most are 32kbps at best. I’m after that type of programming, not music.

All our local sports radio stations are AM but simulcast on the HD2 or HD3 streams of higher powered FM stations their corporate partners own. I can pick most of them up in the car and sometimes in the house. I just need a little more signal for it to be consistent
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post #4 of 10 Old 02-23-2019, 07:51 PM
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Quote:
Originally Posted by cpalmer2k View Post
The problem with streaming is rights issues.. most sports leagues don’t allow streaming now unless you subscribe to their out of market packages. Station streams are required to air alternative programming during games. Most stations in my area don’t have good quality streams either.. 64kbps is a rare thing around here. Most are 32kbps at best. I’m after that type of programming, not music.

All our local sports radio stations are AM but simulcast on the HD2 or HD3 streams of higher powered FM stations their corporate partners own. I can pick most of them up in the car and sometimes in the house. I just need a little more signal for it to be consistent
In that case, since you're picking up the stations but with borderline reception I'd start with the outdoor antenna first before adding the preamp. It's amazing how much it can help just to connect a good FM antenna outside, mounted as high as possible.

Do you have an antenna in mind already? A lot of the great antennas from the glory days of FM have been discontinued by their manufacturers. I don't think you'll easily find an Antennacraft FM-6 today but if you do, I'd grab it. I've read good things about the Stellar Labs 4-element FM antenna which is still available. If you don't want to put a directional antenna on a rotor, then even an omnidirectional outdoor FM antenna might be good enough. Just depends on where the stations are you're trying to hear.

I don't like broadband signal amps very much. They tend to amplify noise along with the signal you're trying to receive. Magnum Dynalab made (or maybe still makes) a line of tunable FM signal amps dating back to the 1980s, but they're not cheap even on the used market. Based on the signal conditions you described I don't think you'll need the preamp if you get the right antenna mounted in a good location, ideally your rooftop.
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post #5 of 10 Old 02-24-2019, 05:56 PM
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Re. FM Antennas: You might want to take a look at my fol. post which summarized the better AM and FM Antennas for Indoor and Outdoor use:
https://www.digitalhome.ca/forum/26-...ml#post2922681
For Outdoors and in Attic I recommend the fol. inexpensive TRUE OMNI Antenna from Stellar Labs 30-2430 which does NOT have Nulls like a typical Bi-Directional "FM Turnstile":
https://www.amazon.com/Stellar-Labs-...lhomconvert-20
My analysis of several "similar" Double-Hoop Antennas revealed that they are not quite Omni (duh...hoops are not complete Circles) with a Gain = -2.1 to +1.3 dBi, and fairly high SWR:
https://imageevent.com/holl_ands/omni/doublehoop

A TRUE OMNI alternative is the Vertical Dipole...however, it is only sensitive to Vertically Polarized Signals, which not all FM Stations are Transmitting, so I can't recommend it for general use [more suited for Low-Power FM Transmitters]:
https://www.amazon.com/Antenna-Outdo.../dp/B000F477AC [Commercial Vertical Stick Dipole]
https://imageevent.com/holl_ands/omni/verticaldipole [DIY Vertical Folded Dipole, Gain = 1.7 to 2.6 dBi]

And I've Analyzed an entire Zoo worth of other FM OMNI Antennas:
https://imageevent.com/holl_ands/omni
The BEST of which is the DIY FM Swept SGBH [but 16.2-ft Tall] with Gain = 4.5 to 7.5 dBi and low SWR:
https://imageevent.com/holl_ands/omn...tsweptsbghomni

IF you decide you want an Outdoor Directional FM Antenna (mounted on top of a ROTATOR), I also recommend using a Manual A/B Switch to select the TRUE OMNI for everyday listening (making it easy to change stations)....or to select the Directional FM Antenna and play around with the Rotator Controls.

Available Outdoor Directional FM Antennas are NOT very plentiful, which include the following:
https://www.amazon.com/dp/B01DWE9I9O [3-Element from Britta Products]
https://www.amazon.com/Element-Direc.../dp/B00HMXX9YW [4-Element from Stellar Labs, less expensive than Britta]
And numerous LARGE All-Band (Ch2-69) Antennas that also have some Gain in the FM Band....which need a HEAVY DUTY, i.e. Ham Quality ROTATOR.

I do NOT advise trying to SHARE the Coax Downlead with your TV Antenna....run a separate Coax. This avoids the extra LOSS (and NOT inexpensive COST) of a TV/FM Antenna Diplexer (i.e. Combiner) and Diplexer(s) to feed each drop. And even more importantly, it avoids sending the FM Signals THRU Mast-Mounted Amps and/or DistroAmps and/or Lossy RF Splitters.

Although it MIGHT improve FM Sensitivity by a couple dB, I also advise NOT passing FM Signals through either a Mast-Mounted Preamp or a DistroAmp. FM Tuners typically come with MULTIPLE RF Tuned Stages in order to suppress ALL Input RF Signals except those within the desired Channel Bandwidth (plus 1 or 2 Channel Bandwidths on either side) which "should" be less than 1 MHz Wide. The subsequent Multiple IF Filters (modern ones are Ceramic vice Wound Coil Type) provide even narrower Bandwidth to suppress Next Adjacent Channels...and perhaps also Adjacent Channel Interference. And fortuitously, the desired RF Signal only needs to be about 1 dB (more or less) Stronger than On-Channel Interference [i.e. "Capture Ratio" spec]. [BTW: Single Stage RF Tuned Stage in older TV Tuners only had about a 10-30 MHz Bandwidth (-3 dB) Filtering capability (more on higher channels)....and was eliminated in most later "Silicon" Tuners....cuz there was no way to fit it onto the Single Chip Implementation for the entire TV Processing Chain.]

When you send the entire UNIVERSE of RF Signals through a Wideband Amplifier [incl. Harmonics of signals at 1/2, 1/3, 1/4 etc of FM Band], Intermod ("Mixing") Products are generated throughout the FM Band....which can NOT be suppressed by the excellent Multi-Gang Tuners found in nearly all FM Tuners....cuz the DAMAGE has already been done....and CAN NOT be undone.

FYI: In an FM Tuner, there is a "Multi-Gang" bank of Variable Capacitors (Varactors in more modern Tuners, manual in old), where one of the "Gangs" is needed to tune the (typ. 10.7 MHz Higher Frequency) Oscillator. Hence my "most excellent" 1971 Kenwood KT7001 4-Gang Tuner had THREE Tuned RF Stages, each of which was progressively filtering out Frequencies other than the desired station:
http://www.fmtunerinfo.com

Last edited by holl_ands; 02-26-2019 at 02:55 PM.
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post #6 of 10 Old 02-24-2019, 06:25 PM
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In fol. post, I provided info about "typical" Analog FM Tuner Sensitivities (Note Mono BW=75-kHz vs Stereo BW=200-kHz difference) at the various S/N Ratio Performance Criteria (NO ONE wants to listen to 30 dB SNR so IGNORE those specs unless you are into DX'ing and only listen long enough to verify the Callsign!!!!). Also bear in mind that it takes a LOT higher signal strength to progressively go from (so-so) 50 dB SNR up to 60 dB SNR....and a LOT more to asymptotically reach the 70 dB SNR Max for my KT7001....and I see that at least SOME Tuners EVENTUALLY reached 80 dB SNR with REALLY Strong input signals [and perhaps switching to wider Bandwidth IF Filters]:
https://www.digitalhome.ca/forum/186...ml#post1369091

Unfortunately, I did NOT easily discover info re HD RADIO [Ibiquity IBOC] mode and would need to dig into various Test Reports a bit further. FYI: Digital is much less sensitive than Analog, even after [optional] Jan2010 increase in fraction of power allocated to Digital vice Analog from a measly 1% up to 4% (6 dB more if Hybrid...but 100% Digital allocation is also allowed). And of course, you won't find meaningful manufacture SPECS for most modern equipment...so there is THAT!!!!

I did verify that FMFool's colorization bands were in the right ballpark, bearing in mind that they are for an Outdoor Antenna with 0 dBd=2.1 dBi Antenna Gain (i.e. OMNI). Increase Signal Level with Gain of Directional Antenna [and Preamp Gain - Preamp Noise Figure, if used]...and [ONLY if NOT using Preamp] Decrease Signal Level by Coax, RF Splitter Loss and Noise Figure of Tuner. Also Decrease Signal Level by about 13 dB +/- 7 dB for Attic/Indoor Antenna [per my analysis of many on-air measurement programs]....give or take some Height Gain differences....and wide range of Construction differences.

A "good" FM Tuner will have a Noise Figure of 1-2 dB [mostly WHY they use a Gain Stage in-between each Lossy Variable RF Filter] and bear in mind that RG-6 only has 2 dB/100-ft Loss in FM Band....so you may only be looking at about 2-3 dB of System Noise Figure vs Noise Figure of Preamp plus Balun. So anticipated improvement of a Preamp in FM Band is MUCH less than in UHF TV Band....if we were to ignore Man-Made Noise....

Per CCIR and later NTIA Measurements, Noise (esp. Man-Made) in the FM Band is 5-20+ dB HIGHER than Thermal Noise....bearing in mind that these are both short-term and long-term AVERAGES, so at any given time on any given frequency, Noise could be Higher....or Lower:
https://photos.imageevent.com/holl_a...%20Nov1992.jpg
https://photos.imageevent.com/holl_a...%20Dec2001.jpg

So improving the System Noise Figure (i.e. Sensitivity) of an FM Tuner installation is likely to be a mostly futile effort, unable to overcome the extremely large Man-Made Noise in the FM Band. And by all means, mount the FM Antenna OUTDOORS, if at all possible, far away from INDOOR Man-Made Noise Sources, such as CFL/LED/Fluorescent Lights and nearly anything with a MOTOR.

Last edited by holl_ands; 02-26-2019 at 03:03 PM.
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post #7 of 10 Old 02-25-2019, 12:04 AM
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BTW: If you are interested in a DIY FM Antenna Project, my fol. post might be of interest, incl. a FM (NOT AM) Double-Hoop OMNI that is "similar" to the Stellar Labs 30-2430...a interesting HIGH GAIN SBGH OMNI....and re-scaling any of several Antennas that I designed and/or analyzed for either Hi-VHF or UHF Band: [I can provide more guidance & info if you choose this alternative.]
https://www.digitalhome.ca/forum/26-...ml#post3054051

And you MAY be interested in trying to track down one of the following FM Antennas (may need to look overseas, but most are no longer available). Or for Dimensions for a DIY implementation:
http://ham-radio.com/k6sti

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post #8 of 10 Old 02-26-2019, 01:48 PM
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Add'l Discussion re FM Input Signal Strength:

As the fol. "typical" Analog FM Mono and Stereo Sensitivity Plots show, the STRONGER the Input Signal, the higher the Output SNR going into your eardrums. Although an Outdoor Antenna with as much Directional Gain as is feasible is the preferred approach [or TRUE OMNI if not] to avoid Harmonic and Intermodulation Noise Desensitization on Weak Stations, if a Preamp doesn't cause problems on the weaker Stations, it CAN improve your Listening Enjoyment on those Stations that are NOT affected by Harmonic and Intermod Interference from the Universe of Strong Signals going into the Preamp. BTW: You MIGHT find specs for your FM Tuner listed here...otherwise you'll have to search for an Owner's Manuals:
http://www.fmtunerinfo.com/specs.html
Note that those FM Tuners with NARROW/WIDE Switching for the IF Filter Bandwidths are capable of much higher Stereo Separation and Lower Distortion.

First two images is the Output SNR vs Input Signal Strength when in STEREO and the third when in MONO. And note that there is a change in performance when the Tuner decides it has sufficient Input Signal Strength to Automatically Switch from MONO to STEREO. BTW: Result for the fol. example DENON TU-380DR and Technics SA-EX110 Component FM Tuners were among the best reported in National Radio Systems Committee (NSRC) Report R37 Part2 dtg 27Jun1999.
https://www.nrscstandards.org/reports/reports.asp

Valuable Lesson to be Learned from these plots is that a VERY STRONG Analog FM Signal Strength of about -65 to -70 dBm is "typically" needed at the Tuner Input in order to provide a very satisfying 60 dB SNR at your ears. [Add Antenna Gain to FMFool Calculated dBm level, Add Preamp Gain and Subtract Balun Loss (and Cable + RF Splitter Losses if Preamp NOT used) to determine Input Level to Tuner.] So, if you do NOT want a Directional Antenna on a Rotator, perhaps I can interest you in a DIY TRUE OMNI Antenna with a Gain of 4.5 to 7.5 dBi:
https://imageevent.com/holl_ands/omn...tsweptsbghomni


DENON TU-380DR STEREO Sensitivity = 60 dB at -65 dBm:
Note MUTING with low Input Signal Strengths until can operate in STEREO Mode



TECHNICS SA-EX110 STEREO Sensitivity = 60 dB at -70 dBm:
Note Automatic MONO Mode at low Input Signal Strengths until can operate in STEREO Mode




DENON TU-380DR MONO Sensitivity = 60 dB at -90 dBm:
[similar for TECHNICS SA-EX110, MONO Sensitivity = 60 dB at -93 dBm (3 dB more sensitive)]



DENON TU-380DR STEREO Separation is Nearly Constant 32-38 dB above -90 dBm:
[similar for TECHNICS SA-EX110, Nearly Constant 36-38 dB above -90 dBm]

Last edited by holl_ands; 02-26-2019 at 02:35 PM.
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post #9 of 10 Old 02-26-2019, 07:46 PM - Thread Starter
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Thanks for all the advice. I think I’m going to try the Stellar Labs omni directional antenna as a starting point and see what that gets me first and take it from there.
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post #10 of 10 Old 03-11-2019, 04:57 PM
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I have found that adding an amplifier to an FM antenna causes the HD Radio signals to drop out. Must be overload or noise issue. And a good set of rabbit ears is a very good FM antenna, and at my former residence in Mauldin, SC it pulled in HD signals for 95.1 and 107.9 from Charlotte. At my new location in Inman, SC I get most all of the Charlotte HD signals, as well as GSP. You should have no problem in Cherokee County.

But there are now interference issues where they have allowed low power stations on the same channel as full power, such as My 102.5 Greenville and WFNZ sports radio 102.5 from Charlotte. And there is a low power Hispanic station on 102.9 in Greenville that interferes with 102.9-WLKO from Charlotte. But my indoor rabbit ears pull in all the main Charlotte HD signals, but there can be dropouts in the car. But 95.1, 96.1, and 107.9 remain strong. I like being able to listen to WBT and WFNZ on 107.9-HD2 and HD3 channels. Also I can get WBT on 99.3, but a Georgia station now interferes in some areas in the car.

But if you prefer a good outdoor FM antenna, then the Stellar Labs models are good choices. As for HD radio receivers, the Sparc HD table radio works good, and the Sangean HDR-18 has a very good HD tuner.
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