N9EWO Reviews :
- Ameco TPA
- MFJ-1020B
Tunable Preamp - Active Antennas

Ameco TPA Tunable Preamp / Active Antenna

The "Made in USA" Ameco TPA Tunable Preamp / Active Antenna (gray plastic cabinet).
Has had a number of changes in production (internal and external).
For it's class, has been the best combination "Tunable Preamp" -
one piece INDOOR active "whip" antenna performer we have ever used.
Sadly discontinued, so it's used market only now.
(N9EWO Photo)

N9EWO Review : Ameco TPA Tunable Preamp / Active Antenna
Discontinued Product
Two samples were tested for this report. (approx. 2002 and 2010 manufacture)
Country of Manufacture: USA
Frequency Coverage : 220 kHz to 30 MHz in 5 Bands
Approx. Serial Number of Test Samples : No Serial Numbers on product
PC Board Marking (second 2010 sample) : Ameco AP-1 / C-1-HB  Rev B-HC
Outdoor Antenna's Used for Testing : Comet H-422 dipole (total length 34 feet long), RF Systems MLB-Long Wire (55 feet long).

- 20 db + high gain.
- Low Noise (as far as these low cost preamp devices go).
- Generally free of spurious signals with 9 volt battery or proper REGULATED power supply (see text)
- Coverage also includes Medium Wave (MW) and a good part of the Long Wave (LW) Band.
- Above average 32 inch whip antenna that is easily detachable.
- Most pleasant unit to tune to proper frequency.
- Easy to read "metal" front panel.
- Large Metal knobs with set screws (first test sample only, see con).
- Standard AC Adapter Jack (DC coaxial 2.1 mm ID x 5.5 mm OD).
- Power "Preamp" ON LED (Red on early sample, Green on later sample).
- PC Board used with later production (see text).
- Cabinet held together using 2 machine screws with brass metal inserts (no self tapping screws).
- Low current consumption (battery miser)

- Limited Dynamic Range. Can easily overload with any long external antenna.
- Ultra light plastic cabinet with no shielding (Color : Black First Sample / Gray Second Sample).
- Uses two “RCA” phono jacks-plugs for external antenna and receiver connections.
- No rubber feet so slides around hopelessly in use with it's very light cabinet weight (easy fix, see text).

- Uses low cost plastic variable capacitor.
- Second test sample used smaller plastic knobs for not as nice ergonomics.
- Ameco P-9T AC Adapter is not included. (optional, see text).
- Earlier production used strange Internal "Point to Point" Construction with no PC Board (looks like a radio made in the 1950's)
- Highly variable quality control over it's years on the market ("Dead on Arrival" samples were common).
- No Schematic Diagram provided in it's 4 page owners manual.

General / Construction and "NO PC Board" Used with Earlier Production

3 knobs (TUNE - BAND - GAIN) and 2 slide switches (PREAMP IN OUT / POWER) with a Power ON LED round out the front panel. All controls operate smoothly, however the quality of the plastic variable capacitor ("Tune" knob) is like what is found in a ultra-cheap $ 2. AM pocket radio. Frequency Coverage is from 220 kHz to 30 MHz in 5 Bands.

With the first test sample (2002) construction is completely "archaic-crude" by todays standards. No PC Board was used and the parts are hap hazardously mounted between the gain control / band selector switch / variable capacitor and the 2 slide switches. Good news is with later production (second 2010 test sample), a PC Board was used and much improved (see photo). The zinger here is the board is ONLY held in place by just the extra heavy gauge wires on the 2 switches, thin wires on the band rotary switch and gain control, plus the telescopic antenna socket/threads if used. There are holes for L brackets on the PC Board (see photo below), but were never used.

Wiring from the two rear RCA jacks to the front panel are made with general hookup wire (no shielded wire is used at all, see internal photo below). Those jacks use a most desirable 2 screw mounting, so less prone of becoming loose. However more recent production went to a less desirable "single hole" mounted RCA jacks with a single mounting nut. Of course this should have been SO-239 connectors for a high frequency SW antenna device.
As it goes with all these devices, the required coax cables to the host receiver and antenna are not included. Highly suggested to use the less bulky (and as flexible as you can get) RG-58 coax cable with no adapters used on the TPA end. This will help greatly with it's very lightweight plastic cabinet (more below on this).
Plastic Cabinet and Knobs

Flyweight plastic case with pretty spartan innards. Front panel is made of metal (aluminum). Just molded feet in the sets cabinet. Owner can easily add stick on "hardware store" feet in short order. Otherwise it will still slide around like a "greasy dead fish" in use. Be sure the cabinet is totally free of dirt and oil before attaching any adhesive type feet (and then allow 24 hours for the adhesive to set before moving it around).

Nice big metal knobs with set screws (first test sample). This along with simple clear front panel markings with the bands, I found this was the easiest and most pleasant box to use of any active antenna-preselector we have ever tested. However with the second sample (later production) a switch was made to the use of smaller plastic knobs (still uses set screws). While ergonomics are still OK this way, substituting larger knobs will help bring back the stellar ease of use.

Appearance also changed a bit over the years. Originally it was in a black plastic cabinet that in time was changed to a Gray color (made in Taiwan). It's lone power LED went from RED to GREEN color. NOTE : A reader has indicated to us that later production runs went back to black color cabinet to late 2019 when it was discontinued. I'm unable to verify this information.

2 bottom (and long) large machine screws are used with brass inserts hold the cabinet together, n
o self tapping screws are used. As they indicate in the manual do not over tighten these as it will warp the top and bottom pieces. But if the screws are too loose the front panel will shift around a bit if the whip in not attached. It is a bit daunting to reassemble the case as the front and rear panels fight each other channeling back into their respective groves. But is not any real drawback (just take your time).

TIPS (for later PC Board Production Samples Only)  :

- With PC board samples this front panel being loose will aid in screwing in the top telescopic antenna. However this is really of little moment as most will not make use the whip anyway.

(However IF you are lucky enough to have a extremely low noise household environment, THEN you may have great results with the included whip antenna. But these days that is becoming more and more of a rare oddity.)

- We hunted down a proper size screw (and length) that inserted into the whip socket in order to raise the PC Board up proper level when the Whip is not used (which will be for most owners). This makes a huge improvement in stability of the front panel and with the collapsed whip (not being installed) will reduce close radio room interference with external outdoor antenna use.   

Power and DOA's

Operation is via a internally mounted 9 volt battery (that is held in place by a nice metal clip) or via a external 9 VDC AC wall adapter. Best to use a regulated type NON SWITCHING type power supply to rule out any self inflicted hum/noise. We used a old linear and REGULATED RadioShack 273-1662A wall wart (set at 9 volts, + tip polarity) and worked good with no hum or buzzes. DO NOT power it using 12 or 13.8 volts (you will be sorry, best to NOT use any unregulated AC Adapters), Uses a rear mounted standard coaxial type DC jack (accepts a 2.1 mm ID x 5.5 OD size plug, long shaft type recommended). Ameco sell (or sold) a matching unregulated AC Adapter for the TPA marked as the P-9T (not tested).

From reading internet observations and comments elsewhere, quality control on the TPA appears to have been a "crap shoot" over its long run in the marketplace. Samples being "Dead on Arrival" are more common then it should be. As it usually goes if any sample operated properly out of the box new, and if it continued to be stable say after a  week or so of use (aside from any owner self inflicted happenings like ESD or RF damage), it was a good one !

Decent Performer for This Class of Device (but don't expect miracles)

The Ameco TPA uses 2 semiconductors (as noted in both test samples) : one - 40673 MOSFET and followed by one - MPS6507 RF transistor. Unlike other Ameco products the owners manual contains no schematic digram.

Has high gain at a tad over 20 db and longest whip (32 inches) that easily beats out the MFJ-1020B/C (see B review below). Not that the whip is all that useful (it really isn't at any length), but is OK for moderate strength MW / SW broadcast stations. As far as I could tell gain was pretty even across it’s range too (this also includes the Medium Wave band which the TPA covers). As it goes with all of these devices, the lower you go in frequency the higher the "Q". In other words you will need to tune more often the lower in frequency you go.

We say "Low Noise" as when compared to other models, but ALL of these devices have some added noise floor and is only made worse with ANY local interference. With it's whip or connected longer indoor antenna (say under 30 feet) gave no overload issues. Use with a better long external outdoor antenna it can severely overload. In some cases with stronger signals oscillation can also occur (as covered in the manual)  Of course just deceasing the "Gain" control tames both of these issues.

Outdoor Antenna as Usual for Good Performance / Now Discontinued (hunt on the used market)

Not everyone is able to have a larger loop or any other antenna outdoors (Apartments / Condos / HOA's etc). One can always carefully "sneak" an extremely thin short insulated wire out a window (at least say at least / over 30 feet / 10 meters or longer) and connect it to the TPA (center pin on the RCA external antenna jack). When you get down to it, f
or this device to work properly in this day and age it really needs to have some sort of a OUTDOOR antenna as high as you can get it and away from structures  / noises and fed with RG-58 coaxial cable (even if again only say a short 30 foot short wire).

The owner must have reasonable expectations with a SW antenna product like this
. As normal local "indoor or outdoor" noise / interference will greatly affect these devices. As it ALWAYS goes with mother nature (storms) one MUST be sure and disconnect ANY outdoor antennas from ALL receivers and / or pre-amplifiers like the TPA when not being used. This is just common sense stuff of course.

Overall we found the Ameco TPA a decent performer after using many of these tuned preamp boxes over the years (as far as these limited one piece INDOOR preselector - whip active antenna boxes go).

Sadly after being on the market for a number of decades it was discontinued in late 2019.

Dave N9EWO
N9EWO, all rights reserved
ver 3.8

Internal photos of the Ameco TPA (later production with PC Board)..
Decent performer, however the PC Board is disconcertingly supported by just the control / switch wires.
 (N9EWO Photo)

MFJ-1020B Tunable Preamp / Active Antenna

MFJ-1020B Tunable Preamp / Active Antenna.
No real horsepower at only <10db gain as an active antenna using with it's own whip.
Best used with longer outdoor antenna's as a active-preselector device.

(IMPORTANT NOTE : We tested the older discontinued "B" version of this antenna)

N9EWO Review : MFJ-1020B Tunable Preamp / Active Antenna
Discontinued Product
Country of Manufacture: USA
Frequency Coverage : 300 kHz to 30 MHz in 5 Bands
Approx. Serial Number of Test Sample: No Serial Number on product.
Outdoor Antenna's Used for Testing : Comet H-422 dipole (total length 34 feet long), RF Systems MLB-Long Wire (55 feet long).
- Very Good Dynamic Range.
- Low Noise.
- Coverage includes the MW band.
- Choice of SO-239 or RCA Phono antenna/radio connections
- AC Adapter Jack (see con).
- Red "Power On" LED indicator
- Skimpy very low gain 10 db gain (or less) when compared to other models (see text).
- All 3 knob’s are small, stiff and hard to adjust.
- Tuning capacitor hard to peak.
- Confusing "Band" makings on front panel.
- Quality control lacking (test sample had crooked front panel and other construction gremlins).

- AC Adapter is not included (extra cost option).
- Short 21 inch included whip antenna doesn't help it's dismal use as a standalone active antenna.

This older discontinued MFJ -1020B model uses 2 semiconductors (as noted in the test sample) : one - 3N211 MOSFET (schematic indicates 40673) and one - 2N5179.

IMPORTANT NOTE : Current MFJ-1020C (not tested) version uses different 2 semiconductors as listed in the owners manual : one - J310 FET, one -  2SC2498. Unknown if the performance is similar to the older B version as tested here ?

If you desire a small amount of gain (10 db if you are lucky) say connecting up to a large OUTDOOR antenna, this could be a good choice, as it’s a nice quiet box of electronics and has decent dynamic range (as it goes with ALL of these boxes the included 21 inch antenna is near useless except for very STRONG signals).
However, if you do find a used 1020B, better plan on replacing the 3 knobs on the front with larger ones. They are just way too small, and also the tuning control is really stiff, The worst of any active antenna ever used in fact. Larger knob’s (with set screws) should help this (not tested) ? To make already difficult ergonomics even worse, the A-B-C-D-E band marking's on the front make the user go ,”duh.....what band I'm I on again?.....” every time you use it ! So make a little 3 x 5 card might help here or use a label maker to improve the band markings (on the Band knob) ?
Nice touch is that MFJ gives YOU the choice on what connectors to use. Either RCA phono OR SO-239’s.

Good for a Pre selector device when being used with a external outdoor antenna. However for use even with a shorter say 30 foot indoor wire antenna as a standalone "indoor" active antenna....we say look elsewhere.

Dave N9EWO
N9EWO, all rights reserved
ver 1.4

Links For Additional Information (all subject to change without notice)

eham Ameco TPA Reviews

Ameco Manufactures Web Page (Milestone Technologies)

Universal Radio's "Ameco TPA" Web Page

Tim Gerchmez's MFJ-1020B Review (from 2000)

Amazon MFJ-1020C Reviews (sorted by date)

eham MFJ-1020C Reviews

MFJ-1020B Owner's Manual

MFJ-1020C Owner's Manual 

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