|
New to Ham Radio?
My Profile
Community
Articles
Forums
News
Reviews
Friends Remembered
Speak Out
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
|
|
Show all reviews of the Tennadyne T10 Log Periodic
|
|
You can write your own review
of the Tennadyne T10 Log Periodic.
|
|
G4OBK
|
Rating: 4/5
|
Nov 20, 2000 03:04
|
Send this review to a friend!
|
|
I would purchase the antenna again
|
Time owned: 0 to 3 months
|
For G3XTT Don Field, Editor CDXC Digest.
This review is one that I wrote for Chiltern DX Club (The UK DX Foundation) November Digest.
I'll post the final part when I've written it and fully tested the antenna. The only problem that I've had so far is the boom to mast clamp which has insufficient strength to hold the antenna firm on the stub mast. "Pinwheeling" occurs at wind speeds in excess of about 40 mph. Tennadyne are mailing me a retro kit so that I can improve the grip of the clamp to the mast. I'll report in the next review if the parts did arrive and if they work. 73 Phil G4OBK
REVIEW
The Tennadyne T10 Log Periodic Antenna - Part 1
Having moved to a new QTH in January 2000 with more space, I obtained planning permission for a 59ft/18m tiltover tower, 10ft/3m long stub mast and two multi-element antennas with a maximum boom length of 26ft/8m.
My main interest in the hobby is working DX on CW, SSB and RTTY on all HF bands, and 50 Mhz. I toyed with idea of purchasing a Cushcraft X7 for 10/15/20m and then stacking it with a Cushcraft A3WS for 12/17m above it. These two antennae are very popular amongst DXers and have been well written up previously. To also stack a 6m yagi on the 3m stub mast was stretching things just that bit too far for my rotator and would have created further chances of interaction between antennas which would mean reduced performance from all three. After a costing exercise on the X7/A3WS, which came out at £853, I did a similar exercise costing a USA made Tennadyne T10 Log periodic. The cost was in US Dollars and had to include UPS airfreight from the manufacturer in Texas, and customs import charges of 24%. At an exchange rate prevailing in June 2000 of $1.48 to the pound, the grand total came to £813.
Brief specification for the T10 LPDA:
Design frequency range: 13-33 Mhz
Quoted Gain measured on antenna range: 6.1 dBd
Front to back ratio: 15-25 dB rising with frequency
Elements: Ten - longest element 38ft/11.6m - turning radius 22ft/6.7m
Boom length: 24ft/7.3m
Weight: 49lbs/22.2kg
Surface area: 10.1sq ft/0.94sq m
Quoted wind survival rating: 100 MPH
Power Rating: Full US power limit
Typical Max SWR: 1.7:1
Half power beamwidth: 52 degrees
Feeder: 50 ohm coax via ?Collins? balun
I started researching the LPDA on the Internet and found that a number of UK based hams were using them. Peter G3MLO had a T10. Frank G2QT had an even bigger 12 element T12 on a 30 foot boom. He had previously used a T10. This I felt was a sure sign that the antenna would be a ?goer? or G2QT would have bought something else. I didn?t expect the antenna to shape up to the performance of a monobander - no multiband HF beam will, however from what these two gentlemen told me I could expect at least similar performance to a TH7 and I could expect it on the 18 and 24Mhz bands as well. G3MLO told me that he had previously used a TH7 and reckoned that his T10 outperformed it. The exact words from Frank G2QT, who in the past has used big quads but now uses the LPDA on account of the low maintenance, were ?It?s too easy with the T12. I rarely need to use an amplifier to work DX. The antenna works much better in practice than it does on paper?. So that clinched it. I ordered the antenna on the internet using Visa on the Wednesday and it was delivered to my door, straight from the factory via UPS, the following Tuesday. HM Customs have a streamlined import procedure arrangement with UPS - the recipient pays the delivery driver at the door, before the shipment changes hands. This saves the nightmare of going to the airport yourself and either paying an agent to clear the goods for you, or doing it yourself ? not recommended unless you have a full day to spare and enjoy studying manuals and filling in forms! I did this in 1994 when I imported a Sommer Log/Yagi. It was a long day - Manchester airport is over 100 miles from my North Yorkshire QTH.
Advantages of LPDA over other antennae:
1. 5 band operation on a single boom.
2. Trapless and virtually maintenance free.
3. No interaction with WARC band beam on same tower.
4. Space therefore created on 10 foot stub mast for a 50 Mhz Yagi with less chance of interaction.
5. Saving in weight/windloading of 33lbs/15kg and 20% less total surface area than on the X7/A3WS combination.
6. Small cost saving of £40 despite the high carriage costs and import duty.
7. No need to switch antennae or use ATU when operating on any frequency between 14-29.7 Mhz.
8. Use of a single feedline up the tower for 14 through 28 Mhz.
9. Broadband design means no compromise was made optimising the antenna design/set up to the CW section of each amateur band at the expense of the SSB section.
Disadvantages of LPDA over other antennae:
1. Greater chance of radiating spurii/harmonics due to broadband design.
2. Slight doubt about the performance of the antenna compared to other options.
3. Virtually impossible to dismantle the 24ft/7.3m boom once assembled.
4. Two nuts to retro fit the tuning stub to the rear of the boom as per the manual were not included.
Summary of Parts:
70 lengths of 6061-T6 aluminium tubing varying from 1? (25mm) O/D down to
0.375? (9.5mm) O/D
4 pairs of aluminium 1.5? (3.2mm) x 72? (1.82m) square boom sections
3 pairs of 8? (100mm) angle aluminium boom splices
14 boom insulator/spacer pieces
2 pairs of boom to mast insulators/mountings and reinforcer plates
68 stainless steel nuts/Nylok bolts
50 stainless steel self-tapping screws
4 washers
U-shaped aluminium tuning stub
Collins 4:1 coaxial balun
14 page A4 sized assembly instruction manual
Assembly/Construction
The antenna arrived undamaged in a strong long white cardboard box. I noted that one of the 4 pairs of twin square boom sections had been incorrectly part marked. The parts however were all present and correct to the Master Parts List (see photo). All bolts and self-tapper screws are stainless steel and no jubilee clips are used in the assembly. The quality of the T6-6061 aluminium tubing looked good. The tubing is quite dull in appearance. Some of the aluminium I?ve seen on other antennas has more lustre and seems to be of a softer grade.
The assembly of the T10 took approximately 15 man-hours spread over two days. This includes the time taken to mount the antenna to the mast and to cable it up. For part of this time I was assisted by my XYL Judy. The only difficult part was inserting the L-shaped angle boom splices inside the boom sections so as to allow the boom to be jointed together, Tennadyne recommend the use of graphite oil and WD40 to allow an easier fit. I used Copperslip compound, WD40 and a length of wood to cushion the blows from a lump hammer. As these splices were an extremely tight fit inside the square boom sections, when they were eventually fitted and bolted together it made the complete boom assembly very strong. The disadvantage being that dismantling of the boom to anything less than 24 feet overall length would be impossible. So don?t buy a Log Periodic to take away on DXpeditions!
The centre part of the twenty elements (10 per separate boom) were bolted into the booms and then the two booms were joined together using the insulators provided. To give further explanation to this you have to appreciate that the Tennadyne LPDAs are fed via the balun at the shortest element on the front of the boom, the twin boom then becomes the transmission line, each side of the boom being insulated from the other. Each element is driven. The design also incorporates a long U-shaped aluminium tuning stub that fits across the rear end of the twin boom to remove any possibility of the boom length being resonant in any amateur band spoiling the performance of the antenna. I reckon that the antenna is more complex to assemble than most HF multibanders apart from the KLM KT34 range, however a methodical approach, following the manual to the letter, paid dividends. The coaxial coiled balun simply feeds the boom via ring tongue tags and is secured to the underside of the boom along with the coax feeder with cable ties (not supplied). The boom therefore is hot with RF whenever you are transmitting. This is why the boom to mast clamp is insulated. The final item to fit to the rear of the boom is the u-shaped tuning stub. Tennadyne suggest that this is fitted when the antenna is complete. Nuts to retro fit the stub on top of the original element mounting nuts are not supplied, however I found some with the correct thread in my bits box and gave them a good coat of vaseline as they weren?t stainless. The addition of this de-tuning stub increases the effective total boom length by approximately 2.75ft/800mm.
The antenna has been on the tower for three days now and first impressions are good. In the next digest I?ll tell you how it measures up and if it did actually perform against my alternative plan of the X7/A3WS combination by doing comparisons with other local amateurs and measuring the gain and F/B ratio from a site a few miles from my QTH.
Copyright: Phil Catterall G4OBK
e-mail: phil.catterall@ntlworld.com
Reference: http://www.tennadyne.com/
|
|
Email Subscription
You are not subscribed to this review.
Subscribe!
My Subscriptions
Subscriptions Help
|
If you have any questions, problems, or suggestions about Reviews
please email your Reviews Manager
|
|
|
